Ding ding ding ding! Hit the nail on the head.
KD found 2 big guys that contributed well - Zeke & Big Dog. He also had a system he could sell to them (by the way, we never made it to the NCAA Tourney with Big Dog). Groce has a system predicated around getting out and running, as well as off the ball movement in the half-court. It's not an easy sell to big guys whom are used to camping underneath the hoop and backing down their defenders.
I think your timetable for the turnaround is completely unrealistic if you're only giving him two years. This program was left in worse condition than I think many of us realized when KD bolted. This roster is looking better and better with each off-season, though, and that's a positive. I know you have a Big Man fetish, but guard-dominated basketball wins not only in the MAC, but at the NCAA Tourney level as well. When's the last time we talked about a mid-major making a run with a big man leading the way? The majority, if not all of the "Cinderella" runs by mid-majors are led by guards. I'm looking at this roster, and thinking "Man, this has all the ingredients to be good." Xeyrius Williams & Sayles are your athletic front-court guys (assuming Sayles doesn't transfer). Riak is your big man. Then your backcourt & forwards (small forwards, traditionally) are all in the 6'2"-6'7" range, which is quite tall and not something we're used to (minus LCJ). This team is going to get out and run teams out of the gym, if they can execute the game plan properly and make their shots (that's the biggest factor). There are a few pieces I'm interested to see how they fit (Ali & Roscoe are the big 2), but otherwise I'm very intrigued.
And can we quit railing on these 1-2 year transfers? Pro sports teams sign vets to 1 year contracts all the time to bring experience into the clubhouse/locker room. If they can play, even better. We have to stop the bleeding and rebuild the culture, though, and I have nothing against a couple 1-2 year players. Groce is at least even with the curve when it comes to the ever-changing & moving landscape of college basketball.