dark knight

[Baynne]

i have an idea i wanted to try out with a fighter or barb with at least 2 lvls of sorc or wizard with focus on necromantic spells. this is for a shadowknight type class. given the spell failure rate, but still wanting some AC... would it be better to roll a barb and wear medium to light armor or roll a fighter and wear plate and suffer the reduce success on spell casts? the main purpose will still be to tank but with the ability to do disease/poison type damage with a couple support buffs. any info appreciated ty