In general, Mana Drain is a crappy mechanic that does more harm than good. Yes, it’s useful on offense, but we have many other tools. On defense, however, it’s the most annoying mechanic in the game next to Devour. (And if I recall correctly, Mana Drain was introduced b/c of Devour. Let’s not forget the rich irony there.)
Therefore, anything to reduce the impact of Mana Drain is welcome in my book. And since the devs have stated repeatedly that they prefer to introduce counters as apposed to properly balance things, they’re not even internally consistent on this point since there’s no counter to Mana Drain.
While we’re on the subject of Mana Drain, I really wish they would revisit the Mana Cost associated with Mana Drain across the board (it’s under-costed relative to its power) while also taking a hard look at Psion’s 3rd trait and at least swapping out Empowered for Fast on Spirit Fox.