Surfaces are great, they really don’t do that much raw damage unless you have a run through a huge one...which seems relatively rare unless you are using barrels or something.
The point about melee being “useless” because fire bolt does 1d6 + 1d4 and then 1d4 from burning per round is also wrong. It’s great at like level one, but even then a fighter can do 2d6+3 in one hit. And at level 4, they can do 2d6+13 with great weapon master.
That’s hardy useless.
Here, you conveniently ignore the HP risk exposure of AoOs and other threats that come with melee range fighting, the massive to-hit penalty fighters take in exchange for that extra damage, you take one of two martial weapons - which are both two-handed mind you - that deal 2d6 damage as the example, and assume that the surface Firebolt ignites will deal damage to only one target. You have to idealize the fighter to compete with an at-will cantrip that is neither gear nor resource dependent.
5E is a carefully balanced game. There are almost no conditions that modify to-hit, and AC spells are few and carefully tuned. Introducing stuff like this might seem fine in EA, but multiclassing will introduce an entirely new level of broken class balance that stems directly from these kinds of thoughtless modifications to the system.
Furthermore, this is not a competitive game, its a party based game, which is played against AI, whether 1 class is "objectively better" than another is not nearly as important as in a PVP game and in my opinion, should not be a driving factor in whether or not something is included..
This is a very silly argument. Video games are challenge spaces like any other type of economic game, individual or not. The success of these challenge spaces, as defined by their appeal to intellectual curiosity and mass consumption, has always been strongly correlated with balanced win conditions and/or game states for each distinct player or element of the game.
Also, Larian's latest RPGs featured PVP opportunities as critically important, story-driving gameplay, so I'm not really sure where this assumption is coming from.