Krieg has a hammer skill that sends enemies WAY up into the air for about 2.5 seconds. His dash S is when he jumps and kicks. His space kicks the enemy (works also when they're standing, sorta like a knockdown with no CD), his ASSSSS is a basic starter, AAAA is a good way to add in a good skill, His S is dmg counter (he gives up 1% of his hp per second, but when he's hit, he gets surrounded by a fog and it massly dmgs the enemy that hit him.
His healings crap BUT HE CAN SAVE LIVES AND CONSERVE MP. His lvl 12 skill allows him to recover 36 hp but he loses 21 hp using it. So he only gains 15 hp. Useless? not really. If your teammate has 0 hp w/ 0 mana, he has a skill that recovers 15 mana x8 and his healing skill will bring their hp above 0, letting them regain mp. Krieg is not much of a tank. He's more of a sweeper and life saver hyrbid (the full would be an eir of course)