I like the idea of balancing multiple masters against activation control. Sure, you could bring Reva, Molly, and Kirai, in the same list, but you will be bringing precious little else and your opponent will get the chance to throw all their ire at one master a turn and bring them down. Not to mention the huge disadvantage you would be putting yourself at in terms of scheme running potential. Plus they will all be drawing on the same pool of soulstones and will thus be much more limited than bringing a one master list built to support them and able to use their soulstone reserve without other friendly masters draining you.