Nobody knows if 310 HP/sec is any good or is useless. We'll have to know how much HP we have and how much damage we're taking at the end-game to really tell. In other words, what this post is basically saying is "energy armor with prismatic armor rune is a nice boost to armor and resistances". And well, yeah, it is. Is it worth it over other armor options? Possibly - It does look powerful. But can't really tell, since we don't know how much we'll actually gain in our survivability when we increase armor by 65% and resistances by 40%, compared to the other stuff we're giving up to get the armor and resistance boost.
As for +20 max AP and +2 AP/sec, am I the only one who doesn't find it all that great? We know how fast AP regenerates and how much faster it regenerates if you use a passive that gives you AP as you use signature spells. Maybe it'll be somewhat good if you run around a lot (making passive regen more important than regenerating AP by using signature spells). But again it's impossible to tell without getting some real in-game experience at the high difficulties. In any case, it has absolutely no synergy whatsoever with energy armor's penalty. In fact, if you think max AP is so great, you might want to consider a different armor or use energy tap. Though again the only way max AP will be that great is if combat is really short and you have plenty of time running around between engagements to refill your AP to its max.
Overall, instead of thinking "how good would X be?" you should think "what should be in-game for X to be good?" and then when you actually play and get some experience you'll need to spend less time thinking what is actually good to use.