Not yet !
In fact, the interrupt must be short enough and fast enough to be sure to not miss the RFM69 interrupts.
The code for 8 dimmers will not be really more complicated : in fact, each time we got a zero cross, we must set a timer to zero, and then wait the good amount of milliseconds to turn on the needed outputs.
So, yes, we'll have an interrupts each 10ms (each time the wave crosses the zero, to be precise !), but I think all we have to do in the interrupt handler is set the timer to zero (or to micros() ...) and then on the main loop, wait the good amount of time for each output before setting them ON.
Seems simple on paper, perhaps it will not work on the chip....
In facts, my main concern is : will the RFM interrupt be short enough to not disturb the zero crossing interrupt ?
Although, not yet tested the RFM : do we NEED the interrupt pin ? Can't we poll frequently the RFM?