Someone brought up Lindsay Ballard a few posts ago, and that is an excellent example of where VOY messed up. Rather than have a long line of recurring characters, who would have pretty steady work for seven years as they popped up from time-to-time (and didn't do a Carey), interacted with the mains, who we got to know and care about over time, they just created her and expected us to give a damn about her from the word 'go'.
I don't see the real problem with this. I mean, TOS only had three main characters and was always pulling new crew members out of nowhere and expected us to care about them. No one complained then.