Sorry, this doesn't help your specific issue, but I have a couple of Linear lamp dimmers and a couple of Leviton lamp dimmers.
I do have rules where more than one are turning off or on at the same time and it does work for me.
I used to have them at different times so each does have it's own rule.
It didn't actually hit me until I started typing this but since I now have some turning on / off at the same times - I'll have to look at doing that with one rule instead of multiple - ie, at 8pm turn on lamp1, lamp2, lamp 5 (instead of a unique rule for each).