Since you only have 1 caster, your physical dps should outdo your magic dps. Have the magic dps go on the MT's soldier while the physical dps burn down the OT's knight. After knight on OT dies, physical dps shift to MT's knight. Magic dps should now be on OT's soldier. Dreadnaught will spawn while soldier is alive, have physical dps focus on dreadnaught after spiders are fed while OT moves on to dreadnaught. OT will have threat on soldier enough by then that the magic dps will not pull it off OT before it dies. Proceed to unload on dreadnaught.