All surfaces (from arrows, consumables, cantrips, and other basic things) should allow a Saving Throw to take 0 damage at the very least. It'd be better if you had to choose: either target an enemy against their AC or the ground around them leading to a Saving Throw, not both. Currently, a single fire arrow can cause two concentration checks immediately and more if you remain in the surface which is way too powerful. The Saving Throw DC of surfaces created from consumables & arrows should be low to compensate for the surface remaining for multiple turns: 10 or 12 at most.
Additionally, going prone shouldn't break concentration. I'm not sure if this is still in the game, but the last time I played it was.
Concentration is fairly balanced in PnP 5e, since there a) aren't that many surfaces, b) typically casters in 5e are in the back and enemies don't exclusively target low-AC characters, c) casters often have mirror image (not concentration) or blur up, and d) feats like War Caster and Resilient are used to improve Con checks. The concentration mechanic does certainly limit the stacking of spells, but that's a whole other discussion.
