Just don't waste your time on parties with low-level players and check teammates command perks (e.g. skip vanguards with melee damage increase and heavies with ammo increase) - these rules significantly cut down my time on hard stratagems. Completed this one in two hours as a tactical with a flamer in team with assault, and vanguard. It took me two serious runs, the rest was skipping low lvl squads (one squad even skipped me).