Skill 1 : For me, it sounds like combination of several skills. Draining max hp is an unique concept but combining it with dmg and maim has made it felt like less unique. Oh wait. This is AoE. No problem now.
Skill 2 : Fervor inspired I suppose. Anyway, nice. Great chasing skill.
Skill 3 : Not really unique. Both armor reduction and DoT is used in DotA (Deso and Orbs). You need STR for ulti but no skill increase it. IMO, you should place STR related skill here.
Skill 4 : Duration should be shorter than 0.5 even on lv 3 or it'll make this hero to have perma-silence. Others are ok IMO