Where the four part MVAM ship has the advantage over four individual ships is when separated the different sections each only carry a portion of the non-combat "bulk" into battle, the four individual ships each have lug into combat everything that make for a full starship, the MVAM ship only needs everything when it's joined.
This is bad math. assuming both sets of four are relative in size, they both have to carry facilities for the same amount of crew. If the MVAM ship carries 100 crew and the 4 single ships each carry 25 crew, it still adds up to facilities for 100 crew total. Now, you could make the MVAM units unequal in size. Have one be the "mother" so to speak. but in that case, just build a carrier for a couple Defiant class ships and be done with it.
MVAM as a ship design is stupid.
MVAM as a tactic
is smart. (which can be achieved with any group of ships)