This is outdated and my MOF has been retired since then. Will update when he gets dusted out
Here is the build I'm currently using on my buff/debuff MOF.
*Note: it is a power build working with owlbear cub so I keep crit as low as possible. If you do not own an owlbear, you should probably go with a crit build. Also, this isn't my main character so it doesn't receive as much investment as it should to be BiS. Companions and mounts are not what you should aim for.
As for anything in life, don't take anything for granted and question/test it
Abilities: Intelligence and Wisdom
Feats: (trying to upload a picture)
Powers: Furious Immolation as daily. Chilling cloud and scorching burst as at-wills. Combustive action and swath of destruction as passives. Fanning the flame (tab), steal time, icy terrain and disintegrate as encounters. I sometime use chill strike and ray of enfeeblement for single target.
Gear: always try to get ArmPen up to have -60 to -65% resistance ignored. I went for power and recovey after that.
Arti gear: I am using the burning MH/OH for increased HP gain thought Twisted and new SKT sets offer more dps. Neck and belt are Valindra's.
Arti: DC sigil, Shard of Valindra, Lostmauth's horn and wheel of elements
Companions: Shadow Demon as active with bonding runestones. It will be replaced by Priestess of Sehanine as soon as I get her gear. Owlbear cub, flame sprite, wild hunt rider and sylph as inactive.