The -dmg only affects it's base attacks, all skill damage is unaffected. The difference in damage is fairly minimal whether you are actually running a beast mastery build or just using your pet to suppliment your own damage output.
The +health makes the pet a target less often, leaving it more free to move. Honestly I don't think it actually makes much difference at all whether you have dire, elder or hearty. Way WAY back before we had so many beast mastery skills (enraged lunge in particular) it made more of a difference, but not so much now.
|