Quote Originally Posted by Apatheist View Post
Renew doesn't stack.

Holy nova costs from 185 mana at rank 1 to 750 mana at rank 6 and does negligible damage (7.14% coefficient.)

In your 20's-30's you'll be OOM in 3 GCD's and you definitely won't clear dungeons spamming holy nova.

There's actually a video of a guy farming with holy nova here. His talent build is entirely based on reducing holy nova cost and he's stacked intellect on all of his gear. He can cast holy nova 10 times before he's OOM -- hitting for around 200 damage per cast. That's 2000 damage plus crits before you're dry. To put that in context, the ogres in Dire Maul have around 14,000HP.
I can assure you that I did work. It's not just theorycrafting - I levelled a team of 1 paladin and 4 priests through SM, ZF and BRD, using just Holy Nova spam. Granted, this was during the TBC expansion (or WotLK - I'm not 100% sure), so I don't know if they did some changes to Holy Nova between 1.12 and then, but I did work - and exceedingly well.

I was never in DM with that team, so I can't say anything about that instance, but I was in BRD at similar level (50'ies - and the elite mobs there have around 8k HP, so thats not far off.