I know the feeling bro. To better fight those damn archers I usually bulk up the Grim Lord's speed so I can avoid them and their arrows while at the same time I can build many portals all around: nearest the portals, better the defense.
Anyway, the main target usually is the Boss, so at the first chance, when I'm powerful enough, I drop into the boss area without thinking too much about surviving. The real deal is my beloved Cornelius Jr.!