Infernalist, altered flesh or hellhound?

Hi, So I have pyromatic pact and 90% fire res in my current build. I'm having trouble choosing between the hellhound or the altered flesh for defensive option.
If my calculations are correct, the altered flesh results in slightly more dmg (if we assume 1000 lightning dmg taken with 75% lightning res, and 90% fire res, with hellhound, only 200 dmg reaches me after resistance + hellhound dmg reduction, while with altered flesh, its 220dmg. Slightly worse, hovewer always active, wich is a bit better in a non minion build, where I don't have any buffs on minion life and such.

Whats your toughts on it? Wich is better? Am I correct in the calculation? (With hellhound, I get the 20% reduction after resistances, while with altered flesh 20% of the whole dmg gets transmuted to fire, then the resistance reductions take place)