There are a lot of noms being thrown out there O_O, here's my take on most of them. (Sorry in advance for the long post)
Vaporeon: B- to C (DISAGREE): I'm probably the only one that's disagreeing with this one, but I've used Vaporeon extensively and I personally think it's still the best Wish Passer over Alomomola/Blissey/Florges/w/e in the tier due to its access to Baton Pass. Slow Wish-Baton Passing is HUGE to heal up other walls without recovery, I've been using other walls coupled with Vap that don't have reliable recovery like Mega Aggron, Doublade, Empoleon, Whims, etc and getting all their health back for late-game with one BP is SO nice. Other Wish Passers like Blissey and Alomomola would be forced to hard switch into the Wish recipient, which could possibly make or break a game at times, whereas Vaporeon could just get the slow BP off. Sure, Vaporeon has to run Protect on all its sets due to the fact it doesn't have Regenerator like Alomomola or Soft-Boiled like Blissey, but I still don't think that small flaw warrants it to drop to C.
Mega Ampharos: A- to B+ (DISAGREE): This is another one I disagree with. I know there are better Megas than Amphy like Mega Bee, Aero, Swampert, etc but Mega Ampharos has some really nice qualities that I feel should keep it at A-. Everytime I play against this monster, I find it extremely hard to switch into to be honest, due to its great coverage and sheer power. STAB Dragon Pulse and (a slow) Volt Switch can do some major damage to teams, not to mention its access to Focus Blast as well, so Ground-Types like Krookodile and Mamoswine can't switch-in confidently (even though Dragon Pulse 2HKOs either way, but these 2 force it out) and to hit Steel-Types like Mega Aggron. But yeah, keep this at A- imo, momentum/switch advantage is huge in this tier.
Toxicroak: A- to A: (AGREE): I think the discovery of the Nasty Plot set was the basis for this nom (Kinda reminds me of the CM Florges set helping it rise to A+), and rightfully so. As of right now in this meta, I think it's the best set for Toxicroak, with its STAB Sludge Wave and STAB priority move in Vacuum Wave, not to mention its ability to run Dark Pulse or HP Ice to donk things like Doublade and Gligar after +2 from Nasty Plot. Here's some calcs demonstrating its power at +2.
+2 252 SpA Life Orb Toxicroak Sludge Wave vs. 252 HP / 24+ SpD Florges: 374-445 (103.8 - 123.6%) -- guaranteed OHKO
+2 252 SpA Life Orb Toxicroak Dark Pulse vs. 240 HP / 16 SpD Eviolite Doublade: 390-460 (122.2 - 144.2%) -- guaranteed OHKO
+2 252 SpA Life Orb Toxicroak Vacuum Wave vs. 0 HP / 0 SpD Mamoswine: 390-460 (108.6 - 128.1%) -- guaranteed OHKO
+2 252 SpA Life Orb Toxicroak Vacuum Wave vs. 0 HP / 0 SpD Krookodile: 346-408 (104.5 - 123.2%) -- guaranteed OHKO
+2 252 SpA Life Orb Toxicroak Hidden Power Ice vs. 248 HP / 8 SpD Eviolite Gligar: 484-572 (145.3 - 171.7%) -- guaranteed OHKO
I think we all know of its great ability in Dry Skin as well (especially with the influx of Bulky Water-Types in the tier), so I won't go into that. But yeah, Toxicroak definitely needs to rise to A
Escavalier: B to B+ (AGREE): Uh yeah this Pokemon is really good right now tbh, I've played around with it on ladder a couple times and its always been extremely effective. The set dodmen posted is really nice as well, but I don't think there's much more to be said, as everything has been said :]. Move this thing up.
Espeon: C to...B? (AGREE): Espeon's speed tier is huge right now, especially with all these Cobalions running around and stuff like that. I has a lot of nice sets atm, such as Dual Screens, CM Sweeper (tears apart stall), Specs, and All-Out Attacker, so it does have a vast movepool. The fact that it can be relatively unpredictable, block status/phazers/entry hazards, AND can break down certain playstyles I think warrants it to rise to AT LEAST B, maybe even B+ because of those qualities
Mega Beedrill: A+ to A/A- (DISAGREE): Considering this Pokemon was brought up for S rank awhile ago, I don't think there's any way that this could happen, especially since the only meta change that happened since then was Hoopa dropping. I think all has been said though, momentum creator, sheer power of Adaptability + STABs, access to Knock off, etc. Keep this at A+
Feraligatr: S to A+ (DISAGREE): Uh yeah I honestly see no way of this happening. SD Gatr can rip apart Stall with relative ease due to the huge amount of power it has at +2 coupled with its Life Orb and Sheer Force. The DD set has the potential to rip apart any playstyle if it gets the opportunity to set-up. After it sets up its almost guaranteed to get atleast 1 kill. Its wallbreaking and sweeping capabilities are too great for it to have a place in A+.
I haven't experienced the other noms (Pangoro, Mega Doom, Nidoking) enough to say anything lengthy about them, but yeah, these are my opinions on the other current noms :]