I recall from the Nexus War questslore that it was imposable for Dragon Aspects to fight each other in person. (Hence why Alex does not participate in fighting maly). There was never a reason given as to WHY she could not fight Maly.
My guess is that if 1 dragon Aspect decides to kill/assail an other dragon Aspect he/she will die in the process.
With this thought it mind I find it reasonable:
Scenario#1: to assume that Alex will sacrifice herself to weaken DW's armor. and that we as hero's get hang around it, while DW implodes. (His power is so big that it can not be contained, without the armor he would implode).
Or
Scenario#2: Alex will sacrifice herself / DW will kill her and Krasus will go-all-medieval-on-DW's-Ass!