You can't determine much from a technical interview. It's best just to ask what they worked on before and explain the new job to them. If people are serious about the job and find it challenging they will stay.
Just think about it. Who would want to lie and get into a job where technical challenges are beyond them? Sure you get a nice salary for a while but then it becomes obvious you are not doing much, you are bored, or can't get up to speed.
The flipside is any firm that can't fire people fast probably has many more issues than just technical interviews/hiring people.
Hiring fast is good sign. Letting go of the appropriate people in a timely manner is also a good sign. Being stuck interviewing people over a span of 3-6 months for the perfect candidate shows indecisiveness or lack of leadership/teamwork. It also means they will spend 3-6 months to let go of that really horrible employee.
Having the team meet candidates means the boss needs signalling from his team to get some type of approval. This is usually a bad sign. I get the whole "cultural fit" concept but it begs the question, besides technical requirements what are you really trying to filter out...
I understand getting buy-in from the team but if your team doesn't respect your choices why are you in charge? Just leave everything to a group vote... There should be some mutual understanding that the current team will respect and work alongside the new employee. The new employee should also understand they need to get involved... If this is not happening you have a leadership problem...