Lion-heart is a very solid dps trait. For me, it is the bottom of the best dps traits. I have not seen confirmation yet that increasing Total Damage would also increase heals or shields, and that makes Aggressive a strictly more desirable trait to unlock through companions. While many people use Lion-heart to get a fine looking hybrid with a solid trait, I would personally not use it very often. I see Brutal and Fierce as being strictly better, and Aggressive is my preference for stacking damage traits. I would not be likely to put all four on a single character, except for perhaps a member of the Tidestorm clan.