Not after one time. I'd say if it's after 3 times. And 10 minute cool down. That, combined with not knowing how far in progress the run is, would be pretty discouraging I think.

Then again, what do I know. I've seen tanks come into CT, see we already passed the boss they need, or we aren't at the exact boss, and they leave. When either way if would have taken less time to get to their boss so they could need and leave, or finish the run with the group instead of deal with the 30 min lock out.