D&D 5E To Allow Multi-Class or Not....A DM's Dilemma

[Uchawi]

If you are unsure about multi-classing, which equates to lack of DM experience on the subject (and is very important for 5e in general), then make class level progression slower. And I mean slow. Then you have time to adjust.

 

[S'mon]

There are two multiclass PCs in my Sunday game. I'd say overall it is a slight power nerf, but in both cases they took a Rogue level to fit their PC concepts. I get the impression 5e multiclassing adds breadth at the expense of a little power. Unlike Feats it is rarely a straight power-up.

 

[CydKnight]

Unless character MCing reduces your enjoyment of the game, stay out of it. If your players want to MC why should the DM get in the way without having real good cause?

Each of the points you bring up should be assumed along with the questions in the OP. The OP is meant to ask if there is "good cause" and, if so, what are some examples.