You are not alone, I have absolutely horrible trouble sparking maxwells against each other. I get it maybe 1 time in 6 ;p
I'll have to give your setup a try - although for the first fight wouldn't you be better off with zelnite->max->elza->max instead of dia ? Zel has a higher dropcount, higher damage, bc drop buff and an instant bc boost...
In unrelated news, my self mandated 1 ticket per rate up got a lord narza. Kind of ehh, but potentially niche usefulness, I guess I level him up ( I'm only summoning so I don't have to use all my crystals on useless crap that will never make a team ).