Seriously. I played a monk, and while Stunning Strike came in clutch sometimes, it was balanced by (a) depending on the opponent failing a save, and (b) using up ki, which will run out over a longer encounter.

Plus, as a DM, I never really had a problem with the players pulling off a huge upset like that. 5e is heroic fantasy, so let them be big damn heroes sometimes. They won't always be! (Though I do play up as though I'm shocked and frustrated, but that's just to play the heel and let them feel extra victorious. :P)

Honestly I support the weakening of stunning strike specifically. The monk shouldn't be crap with the exception of one ability that is so encounter breaking that many DMs are weakening it anyway.

The monk should have been buffed otherwise of course but the modifications to stunning strike are more or less required.

That one of the problems with the design of the Monk class, though. all other possible class features could be argued to be less worthwhile than just using Stunning Strike on every attack each round until it hits, which in my opinion as a Monk player and DM is incredibly boring.