Yeah it's a problem. It is easy/free kills that feeds the other team points, making it a negative for the team.
It's not a widespread problem, thankfully, it seems.
Most people DO have the sense to gear up before trying it.
The ones that do get in with low gear usually get yelled at, and it seems like they don't come back, at least not for a while.

I would support a minimum ilvl requirement as well, but as noted it might be hard to enforce due to class swapping and the buggy Armoury System in general.
But it probably is possible, because they don't let you switch to classes under Level 50, so there are some checks already in place.