I have a question to ask. What kind of runes can i use for my berserker level 20 ? Life or Mastery ?

In the altar i have berserk rage as last point. Tnk

All into life because your finisher gets you the kills and its dealing all the damage that you need without stacking mastery.

Also full life gets you fewer death and you can also survive skyfire or freeze or mortar etc. and fewer death = more uptime = more kills.

Some of the zerks put full mastery to be able to kill tanks with finishing bowl what hard with 2,5 k mastery with full hp( mine). But hp runes a good way too its wich useful vs another zerks.