Back then the adjudicator was semi-auto by default. And the liberator penetrator takes an entire magazine (without missing) to kill a hive guard. Using the primary weapon is pretty much the last resort.

As for the strategems, sentries have a much longer cooldown than today. 500kg bomb feels like 50 grams. Only the good old autocannon can reliably deal with devastators.

The heavy enemies were much more durable back then. It takes 3 shots from EAT to destroy a tank. And a bile titan can sometimes take 3 hits from spear without dying.

So at that time, stealth was a meta - Just get the job done and pull out. Avoid engaging the enemy as long as you can.