Re: @"let alone the distraction for the senior staff."
"My personal experience with project managers is that there is a lot of varience in their technical competence"
You miss the point then.
The JOB of a project manager is to ensure the project is on schedule and on budget. If they recognize their deficienies and have assistants that's fine, but the problem is quite simply that there are a lot f "Project Managers" out there who I'd be surprised if they could organise a drinking session in a brewery without it being 6 weeks late and the drinks being 20 times normal price. (If they can organize it at all)
We've had a number of issues where "Project Managers" were the PROBLEM preventing projects from actually getting done and to a (wo)man they were the ones with the most meetings and the shiniest presentations saying everything was going tickety-boo, oh how wonderful....