@Lucario discussion: Drain Punch. You get it from the Move tutor in Lentimas town, which is late lvl 30s iirc. I think with that he can reach top-tier with that.tbh we really shouldn't factor in Battle Subway / PWT rewards as it detracts from a Pokemon's usability. A base 60 BP / 10 PP until Very lategame where most other Pokemon will have their final STAB moves hinder it. Sure, it can get some nice moves via TM and Move Tutors, but it doesn't replace the fact that it's lacking a STAB move.
[2/3] on Darmanitan. Having the strongest Fire attack in the entire in the game does count for a lot.