I'm about to buy 2 weapon slots and I know I'm going to fill in 3 of them with DA, Polaris, and Blitz, but what should I put in the 4th one. Initially, I thought Shivermist but I realized that I usually run with my friends/guildies who are already seasoned Shivlockers. So then I was thinking Levi in order to maximize damage against his mask phases.
Also, should I get a Crest of Almire for the sole purpose of FSC? I have enough tOkens for a Blackened Crest and upgrading won't be too much trouble of it means I'll be more effective.
I do FSC with DA, Blitz, and Shivermist, even though I use only one of the latter in the Vanaduke fight. It can be useful to have both, to avoid discussions like "Johnny left the party, so we lost our only Shivermist." I've seen vortex bombs used very well in certain parts of FSC. Give one of those a try? But you certainly don't need a fourth weapon.
I got Crest of Almire, just because I didn't have any shadow shield and it's a pretty good one. Now I run FSC in Vog Cub, Vog Cub, and Crest. If you already have a shadow shield, then maybe it's not worth getting.