Certainly stall would appreciate Recover over Regenerator, because Recover is another option that Tentacool would highly appreciate. The choice between the two shifts the focus of the entire pokemon, with Recover making it a stall spinner and Regenerator making it more of a dedicated utility. I think PU overall needs a spinner, and Regenerator helps balance teams and the occasional bulky offense more than Recover would while still being useful on stall. The premise of Tentacool being best on bulky teams is somewhat mitigated by recovery anyway, since Tentacool does not have to rely on its teammates as much as it currently does without recovery.Ben Ohver
Recover Tentacool beats Roselia (AKA best spiker in the tier) 1-on-1 no matter what, which is pretty important imo. Al overestimates the amount of things that can force Tentacool out, for most of the things he mentions can't beat it 1-on-1 when you give Tentacool Recover or are heavily crippled by Scald. Recover is better because it gives Tentacool more lasting power, while momentum loss isn't very important because Tentacool works better on slow, bulky teams anyway, and it's not like Tentacool really needs more than Spin/Scald/Tspikes bar Knock Off, which is nice, but hardly essential. Recover Tentacool seems like it'd be better on stall than Regen Tentacool, and stall would really like a boost in PU considering it's not very good atm. Therefore, Recover > Regenerator
Making a post is too long so going to quote thatBen Ohver
Recover Tentacool beats Roselia (AKA best spiker in the tier) 1-on-1 no matter what, which is pretty important imo. Al overestimates the amount of things that can force Tentacool out, for most of the things he mentions can't beat it 1-on-1 when you give Tentacool Recover or are heavily crippled by Scald. Recover is better because it gives Tentacool more lasting power, while momentum loss isn't very important because Tentacool works better on slow, bulky teams anyway, and it's not like Tentacool really needs more than Spin/Scald/Tspikes bar Knock Off, which is nice, but hardly essential. Recover Tentacool seems like it'd be better on stall than Regen Tentacool, and stall would really like a boost in PU considering it's not very good atm. Therefore, Recover > Regenerator
I don't really know how much flavor Defog has ever really gotten though, it's just kinda a move a lot of things get (see Shiftry, Skuntank, Mew, Scizor). I feel like diversity and relevance over flavor is always important in these kinds of things as well.Peef Rimgar How in the world would a little thing from a Meteor learn Defog? While the move would allow it to be a great Pokemon, it doesn't fit correctly for it to have Defog (Unfortunately).
About the 4 you mentioned, they all have justification. Shiftry can probably flap its arms around with those leaf "fans", Scizor has small wings behind its torso, Skuntank probably learns Defog as something about how skunks release odor, and Mew is Mew and can learn any TM (Defog was one in Gen 4). Granted, Clefairy has something resembling wings on its backsprite as well, but those 4 do have a reason to learn it.I don't really know how much flavor Defog has ever really gotten though, it's just kinda a move a lot of things get (see Shiftry, Skuntank, Mew, Scizor). I feel like diversity and relevance over flavor is always important in these kinds of things as well.
In thinking actually, Defog has a really fairy type feel, at least to me. Maybe I'm weird though