According to the grimiore, Psions are not related to the large cabal in any way. the Cabal are huge as we all know(800-3000 pounds) so they would have no chance in competing against a hunter or warlock in terms of agility and striking speed. So, why not create a small nimble weapon to counter a faster threat? Why not include some of the abilities that thoes nimble treats use such as Blades edge and warlock melee? im not saying titans are slow(physically at least).