The wet condition makes cold and electricity spell overpowered, in my opinion.
That is something that needs to be fixed in general imo, it should give advantage on making the saving throw against the spell, not straight up double the damage taken. It is a bit silly.
Overall, it's just a mess, DOS systems just don't mesh with 5e's systems in a good way. The spells are designed in the ways they are for a reason. Damage dice, effects, etc. They're good enough as long as one doesn't monkey with the parameters of the system, but when one does they need to adjust other parts, and this type of design may snowball into more and more problems. This all results in the mess we've got now, sadly.
I like the idea of surfaces. The only problem I have is that they are not treated like DnD effects. There are spells, that damage you as you move over them etc. But they don't deal automatic damage, but only with a saving throw. That is how surfaces should be treated too.
Basically, you can run through fire as much as you want, but when entering the fire or starting your turn there, you make a dex saving throw, and take 1d4 on a failed one, or none if you pass the save.
That way, they are in line with normal spell effects and everything is fine. Since, lets be honest, 1d4 damage per turn hardly matters, the real problem is UNAVOIDABLE damage, even if it is miniscule, since it triggers concentration saves
