I think the surfaces are more a pain than a help in many cases, tactical strikes with spells are removed if one can only use them when your melee party members are not around the enemy. You'll risk harming allies otherwise. The wet condition makes cold and electricity spell overpowered, in my opinion.
Not to mention, it's an indirect nerf to the Evoker's Sculpt Spell ability, unless the party is also not affected by the surface created by the Evocation spell.
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.
