*sigh*
How about you try and gear your mage properly?
My Pyromancer with a dab of everything did the same and often more dmg than my physical dmg dealers.
I will admit that the other skill lines are abit weaker, but Laser Ray and Firewhip both could easily tear through magic armor turn 1 and whipe them off the board turn 2 if they had weak magic armor.
I keep hearing this about how the mages fall behind the physical, but I had no such issues. I ran 2 mages, and a 2handed tank and a huntsman, everything went smoothly. Yes on classic, and I never used source spells besides the final battle. So yeah, not sure what you're doing wrong but I had no issues.