Usually the player attacking you is in your 3 level range, isn't he? I mean, you shoule be able to at least stall against player within 3 levels of you, and clan should be there to help in case of silence...
Dunno about special cases, if it's invisible I don't see a reason why high lvl shouldn't help...
But in case of red tools - people who attack to break them on own race should be treated with no respect from anyone.
Rule is ofc controvensial and I'd rather my friends could join regardless so +1 But in the matter of logistic point of view, nothing wrong there