My reasoning is simple, the classes shouldn't be exactly the same and have the same utilities. In D1 the warlock and Titan didn't have (until storm trance and hammers) good roaming supers and that was okay because they had (arguably) the best roaming super counter in the nova bomb and Titan slam. Destiny and D2 should essentially be an elaborate game of rock, paper, scissors and if all the classes had the same utility the classes wouldn't feel different or counterable (don't think that's actually a word but you know what I mean!!!!) So by the hunter not having a support ability (which matches the lore and character description) but having the best agility and ability to escape/evade is the right way to be.