I can see that the Optimounts would have a problem tuning if some of the following conditions are met;
1. The batter head of the tom is tuned on the low side and,
2. If the slide mechanism where the vertical tube mounts the tom, is lower than the mid point of the shell, and
3. The angle of the tom is also very high.
4. If your using flanged hoops.
If the above conditions are met, the tension on the top lugs would be high, and therefore would be harder to have an even tension throughout the batter head. The resonant head lugs are in compression, and usually the resonant head is tuned higher so you may not see this effect with that.
Personally, I just purchased an MCX kit with the Optimount for the two overhead toms, and I have just been able to tune the drums. However, I may have the tom heads tuned a little higher than you do so I do not see this effect. Also, I have the cast rims that kind of even out the tuning for all the lugs more than the flange hoops. I am also using a close to flat angle for the toms, and I have the tube mounts towards the top of the shell.