That maynot work.Bcause even shrews wouldn't get 2 turns before gremlin engineers strike. You would need to attack them and kill them first.For that orcs may be required as they are faster.Or your Merc Arc should survive their 1st strike. https://www.lordswm.com/warlog.php?lt=-1&warid=21530281
I was wrong.Hero can't do anything before gremlins strike.Hero can strike first only in knight vanguard.
If my memory serves me right it will get better with higher lvl as the number of merc increases su much, that they won't be killed in the first round by gremlins.
I beat that one at level 5, here is the link. https://www.lordswm.com/warlog.php?lt=-1&warid=15993128
What I do now is split my bows in three or four stacks so you can get lucky and maybe two stacks will go before the Gremlin Engieners.