Concentration Aura is neat, but what exactly are you making instant. There isn't enough to make the effect good.
At the risk of rising A Taste of Divinity prices, I'd suggest priest. Priest got a lot of great tools. Mist of Corrosion is great, but if used incorrectly it can be a one-card Detect Traps. Searing Light gives you plenty of deck building room. And finally, A Taste of Divinity can give a lot of tempo. So, they have new interesting areas to discover and allow for great amount of playskill.
Whereas Paladin decks will look mostly the same (but still require a lot of playskill).
I found myself in a similar situation, but decided on priest because I just played a paladin deck pre-FoH and I don't think it changed much.