I'm sorry, but I have to disagree with you. I've been running Techniciam Loom for a long time on HO teams and it is indeed a killing machine, but his low speed just won't cut it (don't get me wrong, I know it has Mach Punch, but he still gets revenged by lots of common stuff in this meta, like Tornadus-T). And everytime I've ran Techiniciam Loom was to try to find a nice check to Water-types, but it just can't do this effectively because he has terrible defenses, fears getting burned, and has no recovery.
On the other hand, BU Breloom is still a great Water-types check, being able to defeat almost all of them 1v1. He has recovery, more bulk, and doesn't fear getting burned. Switching into water moves (especially Scald) is a quality that Poison Heal Breloom stands out as an effective option, whereas the Techiniciam Breloom takes a bad damage and fears getting burned. And in a metagame where Rain totally dominates, being able to effectively check it is a great quality that this set offers in a much more reliable way.