NERF freaking "Adamantine".
BROKEN REASON #1: At resting state [ADAMANTINE] is already applied in the MMA stance. ADAMANTINE's the one that's causing all the skill negation if the received damage (from enemy) does not exceed 2*the MMA character's MHP. ADAMANTINE will not work if the received damage is OVER 2*the MMA character's MHP, resulting in OHKO of the MMA user. The opponent will be required to WASTE A SKILL and use another skill(effectively 2 skills) in order to be able to attack the MMA character.
BROKEN REASON #2: It is IMPOSSIBLE to deal that much damage (exceeding 2*MMA user's MHP) on a well-geared MMA (in a 1v1 situation). Consequently, the MMA character is protected from the skill and can proceed to use his own skills on the enemy freely. Why broken? There's NO NEED TO PLAN/ POSITION, the MMA character can EASILY rush up to the opponent straight up because the first skill from the opponent will be negated anyway.
BROKEN REASON #3: ADAMANTINE is re-activated upon EVERY SKILL usage from the MMA user (please just look at the very short MMA cool downs, they are SPAMMABLE). The MMA character will be PROTECTED from the opponent's skills every time he uses his own skill to activate ADAMANTINE. How's that fair?
Simple case example in Clique Battle: MMA rushes up to Vanshee Natalie (Adamantine ON). Vanshee Natalie tries to defend herself by casting Deliberate Shot but it gets negated because it did not exceed 2* MMA character's MHP (Adamantine canceled, Toughness activated). MMA is able to get up close to Vanshee to use his skill (Toughness canceled, Adamantine re-activated). Miraculously, Vanshee survives and she tries to shrug him off with Point Blank but once again gets negated because Adamantine was re-activated from the MMA skilling her. MMA uses another skill on Vanshee to finish her off. How is that PVPing? Not to mention with Toughness the MMA can release accumulated damage in addition to his default damage, but that is fine there are ways to go about this BUT NOT FOR ADAMANTINE. Yes there are ways ONLY in mcc3 PVP but a LIMITED NUMBER WAYS and even so the opponent is SEVERELY DISADVANTAGED. For mcc1 PVP there is NO WAY TO COUNTER for 98% of the characters.
These are all mentioned already in Waluste's post. Just reiterating. Please bring this ADAMANTINE mechanic up to IMC and suggest for a removal/ modification. Thank you.