Regarding the initial statement:
I run PI 54 very frequently with my blasters or MM and i am not picky about players levels. In fact I'd take event the bored level 15 player because he can't find a team and i love the challenge. If mobs are too strong and the team cannot make it, then that's the game, but it never happened in hundreds of runs and asides, an occasional wipe is good to raise concentration again 😉
In the end it all comes down to the person leading the group and the willingness to enforce some constraints.