I'm really enjoying Grendel, his enemy-fuelled third and fourth ability give him an unique self-feeding energy economy like Nidus and Hildryn which earns him a special little spot in my Efficiency-abusive heart (That is, the part where I don't feel forced to use Efficiency.)
However, there's a few minor tweaks I'd like to see to give him more Quality of Life.
Add an indicator or wheel for the buffs available and buff selected for Nourish. The icons are hard to discern under duration counters.
Regurgitate could use a counter for when enemies in Grendel's stomach trigger the extra energy drain so you can choose to expel them. I think I heard a minor noise when this happens, but I'm not sure.
Pulverize's speed is very fun going off-hill, but uphill movement and accelerating in tight corridors makes it more prudent to suffer the (long) uncast and recast animations rather than awkwardly wiggling about to speed up again.
Doing Hijack missions with Grendel is an absolute nightmare with his paltry 50 shields. Maybe he should power the Core/Transport with his Health like Inaros and Nidus do.