Tanker Idea, need advice...

Fire does more damage per tick, and Burn possibly could be used to effect in a build like this. But for the concept, until the set is ported to tankers, I can't see anything working better than a Spines/Fire scrapper.

I tried that and found it to die a lot. How do people play scrappers, am I missing a trick to staying alive, lol?

Like tankers need to get into the slotting levels for offense, scrappers need to get that far for survival. Fire and other self-heal resistance sets may not be the best choice for a character that's meant to kill stuff while AFK. But my Spines/WP scrapper is quite adequately tough and will work that way.

Generally, you aren't playing to a Scrapper's strengths with a "go make a sandwich and whittle them down" playstyle. Scrappers have less durability and make up for that with offensive output. Many Scrappers do just fine fighting big crowds of foes as long as they are actively putting out damage and taking down enemies (thus reducing the incoming damage) but would not do so well just standing there sucking up damage and waiting for the aura(s) to slowly melt the foes. Damage output is part of a Scrapper's mitigation.

If you play Spines/Fire aggressively, using the regular click attacks as well as the damage auras, you will find that you still can't stand in a crowd long enough for someone else to make a sandwich -- because the crowd is GONE, baby. That works well enough as a strategy, but it might not be what you want.

You might find something like an Invulnerability/Fire Tanker with Fire Sword Circle set to auto works better for true "wander away from the keyboard" killing.

Note that you'll have to set the attack on auto manually for each fight -- because FSC doesn't need a foe in range to go off, you won't be able to move around a map without the damn thing activating and stopping you in place. :P