Increasingly, the errata can be summarized as:
Player's Handbook [Revision]
Player's Handbook, page 1
Remove Player's Handbook. Replace with errata.
There are a lot of errata. They do improve gameplay, and it's not surprising that many of them weren't discovered before release. Probably, just like in 3e, subsequent prints of the rule books will have these errata integrated, which helps.
It's annoying, but there's not much to be done. I'm still happy they actually fixed stealth! Quite a few other powers were fixed too, Shadow Wasp Strike is the least of the issues.
Warrior's Urging and Come and Get it were fixed to use pull mechanics instead of shift mechanics, which is simply necessary.
Stalwart Guard and Devastation's Wake were nerfed. Stalwart Guard actually makes a little bit of sense now.
Hand of the Gods was fixed (it was a minor action, and it's now a standard action). That's a pretty big change, but it's a multi-marking paladin ability that also happens to boost allies, so that was definitely necessary.
Anyways, just look at how often multiplayer PC games are patched - often for balance changes. Balance isn't easy.