I think that the only problem with the 750 list you've put up is that it's really slow. Nothing moves faster than 5" base besides the Fell Callers (who have to stay behind the champs in general anyway). While in kill-the-caster games this doesn't really matter, it will really hurt in league/SR type games where you need to get to control points ASAP.
With this list you would be giving your opponent 1-2 control points before you were even able to get to the control points. A smart and faster opponent would basically run all his stuff onto the the control points first turn and then feed you roadbumps to stop you from getting to the points to contest them. I had this done to me in a game against Menoth. He went first, got a control point first turn. Then second turn he just fed me waves of Zealots/other junk that I couldn't kill or move past. Third turn I cleared out the zealots, but by then it was too late and he'd already won.
I think it'd be really beneficial to take maybe a unit of Kriel Warriors or maybe even Pygs to contest a point for that first/second turn. Plus, I'm hoping our troll cavalry is good, we definitely need some faster elements for league/scenario games where taking points is really important.
If you won't be playing league games or SR3 scenarios, disregard this post. That is a brutal list for anyone to face in straight out brawls.