Armor is definitely better at all times, but if you want to do the vanguard quests then insignias don't stack with the +armor effect according to wiki so just put on whatever if you want to do those quests. Survivor isn't exactly a great bonus but if its worth the cost of the salvage kit might as well take it I suppose.
I did some math as well (long time ago) about which insignias for charr in the north, +10 armor vs survivor, and it came out that if the fight lasted long enough for the armor to reduce much more damage than the survivor gave to you, you were taking too long to kill them
You are thinking about this the wrong way. Survivor never helps short term, only in near death situations where armor would have helped you more by then anyway. +10 armor will be better at keeping you alive if your base health is at least 200-400 (depending on % of armor-ignoring damage in the area), and it is always better at improving healing efficiency.
Charr rangers are certainly the ones that do by far the most damage in the northlands. Pretty much nothing else compares. As anyone who deathleveled knows (since the rate at which enemies death level goes by the rate at which they deal damage to you), Hunters >>>>> Melee > Casters