What??? Maxed out, his normal attack does 1260 damage. The range increase is why Coiled Snake was released. It sounds to me like your Mortis isn't maxed out and you think that is the reason it's weak. Mortis is one of the only skill cap brawlers in the game, usually played for fun. As a skillcap brawler you actually have to be good at him to push him to high levels (Though I can't compete with Ash or top tiers, I pushed mine to 650+ last season fairly easily as a F2P casual player.
*Edit: Since you have Mortis maxed, why wouldn't you write the buff as "increase attack to 1350" or something like that at max level instead of 1000? It doesn't make sense to me