Why would ferals be behind other tanks in fights with spell damage? Savage defense doesn't work on magic, but neither does blocking or blood shield.
Its hard to argue with DKs having bone shield, ams, ibf, vamp blood, and the oft unused but powerful DRW+Army cooldowns (I've never seen another DK do it, but army gives you a damage reduction to keep you from getting gibbed while casting and thus not avoiding that is equal dodge + parry. DRW gives you 20% more parry, so that's a pretty powerful cd against magic damage, though on a long cd). But compared to warriors and paladins overall our CDs aren't noticeably worse.
We also have a flat 18% reduction on all damage, along with a 6% reduction on magic which meets or exceeds the passive reduction of other tanks. I may have missed something, but pretty sure Paladins have 9% from sanctuary, warriors 10% from dstance, dks 6% blade barrier and 8% from blood pres. Druids can also gear heavily for stamina much more viably than any other tank if being burst down by a melee, magic, melee is a concern. Also the fact that the melee hit right after a magic cast is virtually guaranteed to have a SD shield up since you didn't get hit during the cast doesn't model as much, but it sure is noticeable.
I was mainly thinking about Paladin with glyphed Divine protection? and Warriors with spell reflect ( it it works). Looking over logs he got a bit lower damage from both the spell damage and melee hits. gonna try some regemming for the melee hits, but i'm still unsure about the spell damage (if i can get below the paladin)