Useless tree without Skullfort.
Tons of fun with it (especially with "hands on" perk).
Not something I'd roll with in anything serious, but it's solid for messing around and for Gambit/ Gambit Prime. I'll trade out the strength of the super for unlimited mini-FoH and faster supers in many activities.
But you do have a point that it's basically reliant on one exotic to be viable.
Not really useless.
Certainly less useful, but you still get unlimited throwing knives (if you can get precision kills) and much faster super regeneration from precision hits.
Given the choice, I usually with top tree for the spam clear super (unless it's on brawler, then "playing with fire" in the mid tree is too good to pass up), but that doesn't mean the bottom tree is useless.