4 of of my 5 characters have been 4+ lvs of a single class.
1st PC: 5th lv Fighter (warforged, variant noble, eldritch knight) - dead
2nd PC: 6th lv Druid (1/2ling, acolyte, circle of the land)
3rd (and current) PC: 6th lv Ranger (1/2elf, noble, beast master)
4th (and favorite) PC: 8th lv Warlock (1/2ling, far wanderer, fey patron, chain pact)
5th PC: 2nd lv Fighter (human, criminal, has the magic initiate feat, will probably become an eldritch knight)
*I briefly considered MCing the warlock - into wizard - for story reasons. Fortunately the situation that prompted that consideration got resolved to my liking & I didn't have to do that.
*I'm strongly considering MCing the human fighter into warlock eventually. Maybe sorcerer? Not for any real power advantage, but because story-wise thanks to his past criminal activity he's got a bit of a fire spirit (fire elemental?) fused into him. This is already the source of his Magic Initiate feat (manifesting as fire based effects). I'm thinking that the longer he's carrying this spirit around in him, the more it'll influence him. I'll have to see how things play out.