Frost wyrms are worthless if you are slow as shit... but if you desperately need/want to go for frosties... get 3 heroes and creep while fast teching with lotsa D... but good god help me dont mass frosties for solo... you'll get owned... but yeah, I'd say necros with ghouls are the way to go. Just a reminder, micro is really important... if you are just getting necros for skels... dont even bother playing.