At what point does Stakeout become busted?

One of the best abilities to be bestowed upon purely shitmons, Stakeout would undoubtedly be OP on some higher tier threats, but where is the cutoff from it being balanced to being broken?

Mobastiff has a respectable 120 attack and 85 speed, alongside excellent neutral coverage, yet is still completely unviable in higher tiers. Given this ability is best on Choiced wallbreaking mons who crave immediate power, I’d imagine Swords Dance and weak priority wouldn’t necessarily push a Stakeout mon over the edge, though dual 100+ BP STAB with near perfect coverage might.

But if that’s the case? Then what mix of attack/speed is reasonable? On the one hand, 120+ attack/100 speed with perfect neutral 100+ BP STAB coverage sounds like it could be too OP. But while reducing that to 100 attack sounds reasonable, then it can’t wallbreak unless the opponent switches out, greatly diminishing its general utility.

So where do people draw the line? I feel like 100 base speed is the upper speed limit and 100-120 attack is the sweet spot, but where exactly in that 100-120 range do people think? Would something like Tinkaton be balanced with it by having an auto delete button every other turn but middling attacking stats otherwise and inability to run a Choice Band/Scarf? I know Stakeout was banned in AAA, so any insight from what made it broken there would be greatly appreciated.