I figured it'd make sense to make one like this so BAM. I'm currently stuck on the first snow mission, facing off against Baldren Gassenarl, and his seemingly infinite range. I'm sure it's just my ineptitude, but I can for the life of me figure out how to juggle the logistics of it all.

I remember that one being a pain, the way I did it was to just spread my army as thin as possible, 2 units in each area. That way Baldren would keep switching between areas, since he could only wipe out one duo at a time, it let my other duos advance in their sections. I took just the deaths and kept moving forward. Also use the construction arm on your tank to build that ladder at the start, gives you an easy way behind them, spreading even more.
 
However the easier way is to just kill him, lure him inbetween a tech and a sniper. Since he dodges most attacks from the front, put the Tech in his face, then from a safe distance (behind sandbags) snipe him in the back of the head, he will turn towards the sniper, then use the Tech to smack him in the back and repeat until dead.

I found that mission became a bunch easier after defeating Baldren.