Imo, the knockdown attribute is NOT worth it, it increases the SP COST of Smite by 8 ( 37 - 45SP). I’d rather just stack them up and double smite them.
I don’t know about other itens that increase AOE ratio, Caedes already talked about it.
Here’s my skill build : http://www.tosbase.com/tools/skill-simulator/build/237au8aori/
I chose to keep Restoration at lvl 1 up untill the last few points you get. Investing skill points in it just doesn’t seem rewarding. Gaining +337 HP recovery looks good, but all in all, restoring +337 HP every 15 seconds isn’t going to make a difference when you can Heal up to full every 20 seconds.
Resist Elements Is a MUST at 15. You gain extra chance to NULLIFY ELEMENTAL DAMAGE and that’s just OP, imagine PvPing a Wizard, you have 15% chance to completly ignore his attacks.
Get Revive lvl 2(or 3 if you don’t want Monstrance to buff your party’s DEX for some reason) and Mass Heal lvl 1 : Revive is actually OP, you not only AVOID DEATH, but you also come out with 10% of you HP AND 2 seconds of invincibility, that’s most likely enough to get yourself healed up to full and you can keep it always active if you invest a few points in its attribute.
Mass heal is good enough at lvl 1, the amount of HP recovered from lvl 1 to 5 only goes up from 20% MHP up to 28% MHP. I don’t think this has a higher priority than Revive.