The only place DDO has slaadi so far is the end fight of "Subversion", and its crazy tempo makes it hard to pay attention to Combat tab. So far I only played this quest on HN, HH and HE, and as far as I can tell slaadi have crazy high (for heroic) Cold resistance, but not complete immunity. They have some Lightning resistance, and (I think) no Fire resistance. Axiomatic weapons were showing purple numbers -- evident alignment vulnerability. Can't tell if they are chaotic evil or chaotic neutral: a sword of Pure Good was doing Good damage, but that does not prove anything, as PG affects neutrals. I did not have any Holy weapon to test out.