The lack of efficiency in killing to it's ammo is, if anything, probably because of it's LoS issue. The initial cold procc will often hit all enemies in the zone, but the actual AoE will only hit a few, or none at all depending on what it sticks to in the environment.
There's no reason why it should be struggling to kill compare to it's ammo count, it has nearly 11m radius as it's 'AoE' with Firestorm, and the stats are good (albeit Status Chance is still kinda low, it's workable with Multishot factoring in too).
If DE makes the Lenz AoE work properly like all AoEs are right now, then it'll be worth using. I would very much like to use it as I'm an OG Lenz fan, but until then, I might as well use a Gas Daikyu, it'll kill the same amount of people if not more in 1 shot, and not have AoE ammo-issues.