As a general rule, it is worth going into the warrior tree even as an assassin to get offensive stance, marauder, and blazing strike. Crushing blows and invigorate are also good talents but as a Dps, you don't need more than one person in a group to have them, so you could leave them off if you plan to go with others who do have them.
Whether you do medium or heavy armor depends on what you want to do. For PvP, I think heavy has an edge up. For Dps'ing dungeons, medium has an edge up. Medium is better for soloing CC bosses as well if you have good enough defenses to solo them anyway. At that point, you should focus on dealing more damage and hence, go with medium armor. On a side note, for those who want to use a two handed weapon (a warsin), I would recommend using heavy armor even as a Dps.
My sinwar build for Dps'ing dungeons is the only build I am not willing to share entirely but I will link as much of it as I feel comfortable sharing.
http://TalentTheory....u2B1C1I2N1O1Q2/
Edited by Elrog, 19 March 2017 - 19:14.