Well, I've only played one Dota game so I can't really make any comparisons
To answer your question, it's really only been this season (that I'm aware of, only been playing since start of S5) where things have really fluctuated this much. If you haven't noticed, they've been completely changing the game this season with
- Entire ADC rework
- Upcoming Mage Rework
- So many AD/Tank items it could be considered a Tank Rework
that in itself are the 3/4 main types of champions (assassins have only been changed slightly in comparison). With Riot completely changing how things interact with each other in the game. Not only that but we've had a decent amount of champion reworks and releases recently as well. It'll take some time until things become as "balanced" as they were before.
People don't credit Riot enough, they've been trying to do a lot this season to change up the experience for players. Has it all gone perfect? Nah, of course not. But we can't expect changing league so much to be done perfectly in a short amount of time can we?
IMO, leave Riot be to figure out how they want their game to be. We're here for the enjoyment, none of us are on the board of committee or anything like that, we're here to play the game.