When speaking about Heatran in ubers, what comes to people's mind is that Dialga overshadows it in every offensive regard, which is true.
If you opt for a powerful Life Orb sweeper chose Dialga, because Hetran has almost no means to be an effective sweeper in ubers. while Dilaga has access to Dragon Stab moves Thunder and Fire Blast, Heatran can't compete with it only having Stab Fire and Explosion at its disposal.
Therefore Ubertran must fill rather defensive niches which haven't been explored yet.
I hope I can give you some ideas of teammates and play style that would appreciate Ubertran, enjoy.
As I have said before, offensive Heatran is rather a poor option compared to Dialga, and this applies to the Scarfer too. Heatran, however, can run a Choice Scarf as well, why I will mention this set before doing the main analysis of defensive Ubertran.
@Choice Scarf
Ability: Flash fire
Evs: 4HP/252 Satk/252Spd
Hasty Nature(+Spd, -Def)
-Fire Blast
-Dragon Pulse
-Hp Rock
-Explosion
This set differs slightly from CS-Dialga, while latter is a solid option to check SD-Quaza and Lati@s, as well as Darkrai and Skymin, Hetran can fit in teams that are weak to Ho-oh and need a fail-safe against SD-Ray, CM-Mewtwo, Darkrai and Lati@s. It has access to Explosion which is great against those, but also its downfall, since it must Explode quite often to take them out, while CS Dialga has better over all stats and means to kill these threats with its Stab moves. However, this Heatran can fit in lots of teams and works well, just don't exspect it to be a good check against dragons.
Ubertran
The real reason making Heatran an intriguing option in ubers is its ability to spam toxic, tank the most common offensive move in ubers(dragon) and keep steels, immune to toxic, off the field.
To prove its effectivity I have made following calculations: First off we assume the uber tier mainly consists of pokemon with a significant usage(that means 5%+). Second off we extract those pokemon who can't be touched by toxic(rest, safeguard, natural cure) which happens by percentage too(for example 30% of all Kyogres have the move rest). Then we add Forrtress and Scizor to the list of pokemons that are touched by Heatran due to their 4*weakness to its main Stab.
The result is quite amazing: Toxic+Fire Move provides you with a 90% effectivity in the current Uber metagame. Among the 10%, 80% is contributed by Blissey and BU-Dialga.
Finding a way to effectively deal with these two will bring you great success. The first set I will introduce you to, has found a way to deal with Bu-Dialga while still packing enormous bulk.
@Life Orb
Ability:Flash Fire
Evs: 252HP/252SDef/4SAtk
Calm Nature(+SDef, -Atk)
-Fire Blast
-Toxic
-Rest
-Sleep Talk
Life Orb allows Heatran to ohko standard Taunt+CM Mewtwo and to 2hko BU-Dialga in the sun. +1 Outrage from Bu-won't even 3hko you, while you can comfortabily 2hko it back and effectively eleminate a toxic taker.
CS-Dialga will possibly suffer a ko in the sun, Fire Blast will do 92.38% - 109.09% to it. So only Blissey and resttalk Kyogre left to deal with.
Note that this Heatran CANNOT wall any Ho-oh that has max attack and LO, since BB will 3hko then. This set is very effective when paired up with a Groudon(bulky is appreciated), since it will be able to wall any Lati@s without Refresh/Safeguard(don't worry these two moves aren't even listed in the usage list). Surf won't 3hko it, so you can toxic them and rest until they die. Mixed Dialga will have a tough time against this Heatran, unless it has the very rare Earthpower or Brick Break.
Sample Team:
Groudon @ Chesto
Ability: Drought
EVs: 252 HP/112Def/16Spe/96SDef
Impish nature (+Def, -SAtk)
- Stealth Rock
- Earthquake
- Roar
- Stone Edge
---
Forretress (M) @ Leftovers
Ability: Sturdy
EVs: 248 HP/8 Atk/252 SDef
Careful nature (+SDef, -SAtk)
- Explosion
- Spikes
- Rapid Spin
- Payback
---
Heatran (M) @ Life Orb
Ability: Flash Fire
EVs: 252 HP/4 SAtk/252 SDef
Calm nature (+SDef, -Atk)
- Toxic
- Fire Blast
- Rest
- Sleeptalk
---
Giratina-o @ Platinum Orb
Ability: Levitate
Evs:252 Def/196 Spd/60 SAtk
Timid nature (+Spd, -Atk)
- Stone Edge
- Draco Meteor
- Hidden Power [Fire]
- Toxic
---
Palkia @ Choice Scarf
Ability: Pressure
Evs:4 HP/252 Spd/252 SAtk
Timid nature (+Spd, -Atk)
- Spacial Rend
- Surf
- Thunder
- Fire Blast
---
Mewtwo @ Leftovers
Ability: Pressure
Evs:4 HP/252 Spd/252 SAtk
Timid nature (+Spd, -Atk)
- Aura Sphere
- Ice Beam
- Calm Mind
- Taunt
---
Groudon brings the sun, which is essential for Heatran, while Palkia can tank Kyogre's water attacks. Mewtwo is a nice pokemon to finish off Palkia, Latia@s and Kyogre when they have been weakened by Toxic. It can taunt the bulky resttalk Kyogre when it is asleep(which is likely when it has been poisoned) and get one more CM without being hurt by Surf. Forretress is the best way to deal with Bliss, but you could use a Skarmory too, since Heatran outstalls Bliss and will cause many switches. Skarmory is a good partner because it can wall EQ-Quaza, while Heatran can take on Overheat-Quaza. Note that this spread won't protect you from SD-Quaza as a +2 adamant Outrage has a chance to ohko it. The fact that it has to use Outrage to beat you down before dieing of toxic and lo-Fire Blast is quite amusing though.(+6 espeed only 2hkoes it).
But Heatran isn't restricted to be a special wall, it can run some utility sets too. May I introduce you to an old friend from Ou:
here comes Shuca-Tran
@Shuca Berry
Ability: Flash Fire
Evs: 252HP/168Def/84SDef
Relaxed Nature(+Def,-Spd)
-Stealth Rock
-Fire Blast
-Toxic/Explosion
-Explosion/Hp Rock
This Heatran will never be koed by Eq-Hooh nor SD-Quaza(even adamant can't) so that you can blow up in their faces and see the surprise.
It might not work as a lead in ubers, but has great utility in teams that have a sweeping Groudon and thus need Stealth Rock as well as some protection against Hooh, Heatran can come in on Sacred Fire and use either Hp rock(does about 60% max.) or blow up on it. It can beat Sub Roost Ho-oh by playing the hp rock-toxic game, and set up Sr for you. A rock Polish groudon would be the best partner for this Heatran asit can blow up on things like Bulky Resttalk Kyogre or Latias, who can be very annyoing to Groudon.
Counters:
Of course there are some Pokemon Heatran does not like to face:
Giratina with resttalk is the worst nightmare for any Heatran user, there is just nothing you could do about this, it drains your pps and laughs at your assaults. But there is hope, Giratina is very rare nowadays, and the new mixed Giratina-o is toxic stalled by Heatran and not the other way round.
Blissey can be annoying as it can try to drain toxic's PPs, but spikes will make it less annoying.
Opposing Heatrans can be VERY annoying, but when did you see one for the last time in Ubers?
Refresh Lati@s can fool you, so watch out for these. Safeguard must avoid to switch in Toxic, and is quite obvious as it will use it before it sets up on you. Safeguard Lugia can annoy you, but is not able to do anything back.
Entry hazards are your best bet against most of the mentioned counters.
Team options:
-Groudon is a must have for every Heatran user, it will help it take on almost all special focused Dragons, and allow it to ko Mewtwo and other rather frail sweepers.
-Palkia/Latias Every team based on the sun needs them, because Kyogre is still number one in usage, and you don't want to get swept by it.
-Celebi: The famous combination Celetran could make its way to ubers:
Celetran can stall so many Ubers, it's not even funny, which set you chose is up to you, my advice is Leech Seed and Hp Ice/U-turn on Celebi and restalk, toxic on Heatran. Celebi can effectively deal with water moves(note: modest full powered watersprout from specs-ogre will 2hko)
as well as with Earthquake.
-Skymin/Jumpluff Both work similarly to Celebi, but are rather frail and fear even not very effectif moves when they are fired off by Kyogre or Palkia, they can switch in on EQ though, Jumpluff deserves a special mention as it can encore the previous attack.
-Mewtwo: really likes to sweep through teams that have been softened up by toxic, especially when Palkia and Kyogre are in a weak condition.
-Rayquaza: If you are crazy enough use this little baby in your stall team and switch into CS-Palkia's surf
-Ho-oh: This might seem weird at first glance, but Ho-oh is an excellent addition to Heatran as it can take on all attacks Heatran does not like(exept for surf), it can easily predict a switch to Blissey too and set up on it.
Conclusion:
If you like sunny weather and have a Groudon in almost all of your teams you should really try Heatran. It can easily do Blissey's job without being bothered by Forrtress or Scizor. Celetran is very underlooked in ubers, and can easily decide a match, you will find it very hard to break through a combination of Celebi Groudon and Heatran.
On the other hand, if you are using rain don't even bother testing this Heatran in your team it will never work. Its true home is a balanced/stall team with Groudon.