And on top of this, against degenerate OTK combo decks, which are far from rare in Wild, Reno is nothing more than a 6 mana 4/6. It doesn't reset anything when your opponent has no interest in killing you with chip damage.
Stealer on the other hand, is overpowered every game.
Chip damage is, 100%, important to a lot of OTK combos. It allows a smaller/safer combo turn if you've chipped your opp down to 22ish. Same as freezemage's gameplan against Renolock before wild; chip away, get burst heal used, then go for things, or simply burst from 22ish. Now, Freeze didn't OTK that often, but any maly-based OTK will be similar. I tend to play janky OTKs (Malygos shaman is my main deck, though I've used hunter before, too). Reno also walls these decks when paired with IB, which is annoying, but that's hard counters for you.
Stealer and Reno, however, really can't be compared. Reno is very different - I feel it's bad for the game, but it's an idea that blizz really like, and it's for a very different reason that I dislike it:
1) Burst healing of that magnitude adds variance based on drawing by T6 against aggro, and the entire singleton mechanic adds variance.
2) Burst healing, particularly to the extent where you've got Raza priests healing to full four times, which I have seen before, pushed towards OTKs, which most people dislike. So much healing just obviates control because you will struggle to kill without OTKs.
3) Singleton decks being pushed means less control tools can be printed, else the singleton decks lose their drawbacks. This pushes all control builds into playing singleton, which we saw pre-wild's creation. This has been solved to some extent by Wild existing, but rears its head every few sets when they push the mechanic in STD, but is part of why I feel it's a really bad design decision by Blizz to create such cards.
However, Blizz like singleton decks, as do the community, so all I can do is build around it as much as possible.