Sat Dec 10, 2016 7:38 pm
The stat boost actually vary depending on your faith, and also the max potential of the hero involved, so its difficult to give a definite answer.
From the Gallery, I've managed to calculate that a +2 hero gains about additional 20% - 50% per stat at mlb. Of course, the 50% comes from the already lowest stat of the hero, so its not saying much. Still, a 20% gain from mlb for the highest stat means that each limit break gives about a 4% bonus, so for a guardian class, that's like 400 bonus HP right there for a 5*, but only 250+hp for a 4*, before we involve other stats, or maybe rune effects, etc.
As such, if you can mlb a 4*, it would be best to go for the mlb, but for 5*, which are more difficult to mlb, it may be useful to study the other classes and their skills. Those skills and auras MIGHT just help you out of a tough situation.