Drk tanking without Darkside.

[Alistaire]

Possibility #1: The player couldn't into simple MP management, so the mp was spent and Darkside automatically turned off, forgot to turn it on again until the boss.
Possibility #2: The player couldn't into simple MP management, so they opted to just not use Darkside on trash and decided to use it on boss only instead.
Possibility #3: It's my subs I can play however I want.

Or 4, you're in Haukke Manor or Brayflox normal where you don't have blood price making fulltime use very cumbersome.