Chad is the team's tank. Able to take on lots of damage (Like falling from Kuukaku's spirit cannonball thingy). But only able to do slow, linear, attacks.

Think as the whole Bleach thing as a traditionnal Rpg game.
You got Mainchar Nuker (Ichigo), The Tank(Chad), The Ranged(Ishida), a Healer(Orihime but Renji is making up for the gap), a MagicSpecialist(Rukia) and all the side chars.

But hey, if the fact that being in HM boost Chad's powers; we may get a "Pocket-Zaraki".