You have to be in lvl 5 clan with learned clan skill. Skill costs 0 rep points and 1 Destruction Tombstone. But your clan have to have positive reputation points for the leader to be able to learn clan skill.
Considering I don't think raid points do anything...
...does it matter?
Yes, DDs get to feel as though they have the bigger [censored] with a higher rank, but shouldn't tanks and healers already be used to this...? This is L2, after all.
You can learn the clan skill with a lvl 5 clan. The raid channel is the same thing you had in C4 where clanleaders could do /channelinvite <partyleader>. With the skill, all clanmembers are supposed to be able to do it. Dont think it spreads the points, though as we had a raid channel going last night and the tank party got less raid points than the DD parties.