I haven't finished leveling my MCH so I can't confirm this so someone please correct me if I'm wrong.
The Rook/Bishop turrets, when hypercharged, apply a Phys/Magic Vulnerability Up debuff to the target/targets respectively for the duration of Hypercharge. Is that a thing or am I talking shi*?

If the above is true, then MCH has comparable utility to bards.

Regen (TP/MP)
Vulnerability Up +5% (Phy/Magic)
Reduce Damage Dealt -5% (Phy/Magic)
Stun/Silence