Remove unavoidable crowd control. CC you cannot avoid is frustrating, and never fun. Give every CC ability a visual/sound effect, give jailer a delay, give nightmare a travel time, etc. Frozen is a great example of a CC that works well, its potentially very dangerous and can be avoided.
Make event rewards worthwhile. 820g is in no way a sufficient reward for completing these tasks. A Resplendent chest/rare pack per event should be mandatory. Completing an event should always provide a stack of NV.
Increase Resplendent chest spawn rate. I don't know what happened to the resplendent chest. I started playing the game a few weeks ago after a hiatus of a few months, and I've found two since I've come back. Both were in act two, haven't seen one in any other act (and I've been farming keys, so I've been running most acts). I know that they were ruining the economy when the game launched, but they can't be making a difference now - buff their spawn rate/locations back to what they were when the game launched.
It's a Trap!
Introduce more environmental effects (Traps, mines, summoners, etc). The ones currently in game stop providing any challenge at all past MP 1. Consider augmenting the damage of these traps, instead giving them a wide range of potentially long lasting, potentially stacking debuffs. If you currently ignore the game environment while farming, this could provide some form of challenge which keeps you focused on where you are, instead of just on how many mobs there are on screen. This could also provide more tactical opportunities against particularly difficult elite affix combos.
I have never agreed that there should be penalty for changing abilities during play. If a player wants to waste 30 seconds to a minute changing their spec before they fight a particular affix combo, why should this affect their magic find and gold find? It already takes them longer than someone who just sticks to one build for the whole session, especially if they experiment with builds on the fly, which was something I had a lot of fun doing before NV was introduced . Why should they suffer magic find penalties, gold find penalties, and clear time penalties? In order to engage an elite strategically, you need a build which exploits the weaknesses of their affixes. Allow on the fly change, keep the minute ability swap CD (for clear time penalty) and let players keep their NV stacks.
Introduce more content, more regularly. Biggest issue I feel with the game; there's nothing to do but farm items and paragon levels - which, don't get me wrong, is what the game is all about. However, if I'm not looking forward to events and I've been stuck in act three for months (OK, so personally I haven't, but I understand that to be where most people are farming; could be wrong), it might be nice if there were new items constantly being added to the game, or new content like more dungeons (which, I guess, is being addressed with monster density changes in 1.0.8, because we'll have incentive to farm acts other than the third).
I'm not talking about introducing new tiers of items, but perhaps a shift into some purely aesthetic items? Introduce a new slot for items which just change the look of your character and give each boss in each act a different one, and some special ones that only spawn in event locations (Like a chicken hat which is guaranteed to drop from a chest at the end of the fowl lair, for example).
Conclusion (TL DR):
Adjust some of the unavoidable CC, buff event rewards, buff resplendent chest spawns, buff environment traps, remove ability swap NV penalty (keep ability swap CD penalty), release more content more often, introduce a new form of visual augmentation dropped by specific bosses and events.