The reason I used the combine animations for the grunts was because the old grunts animations didn't have the 360 degree movement blends and a lot of other stuff that look way better. Plus Romka, being the pro that he is, did all the vertex weights and used the HL2 humanoid rig. I could never redo the weights as good as he did, so I wouldn't try.
I like the grunts, I think they look amazing and their radio commands make me all nostalgic about hl1. I think they are ok in combat the ones in hl1 were quite simply Aimbots i.e they dint miss yoiur head often, thats all that made them tough. lets face it combine aren't the toughest either. I think the grunts just need to be placed with a bit of thought by the map maker. Also most of the grunts you encounter in hl1 is in the first half of the game when you have the smaller weapons like pistol shotgun and smg!