I think a lot of people are blowing WWI and the weapons used out of proportion. Sometimes areas of a front would be under a few days non-stop bombardment and when the enemy came forward they were still defending their trenches. Things are a bit more survivable than you think, but certainly much more deadly than NW.
If you've ran through MG42 fire in any WWII game or dodged HE from a tank, those are a lot more deadly than inaccurate artillery strikes or a Maxim.
Big units are great for organizing, but even they need to have a chain of command to perform varied tasks with success. Instead of saying "10 guys stay behind and cover our flank" wouldn't it be easier if you said "1st Squad" and not have to hand-pick people every time you needed to allocate a task in such varied and deadly terrain?