Yes it is normal that you spend most of your time trying to Cast CCs. Yes best Materia is where each item is Spell Speed capped. No you don't need other cross class skills other than Arcanist and Archer. Relic Weapon is better than Crafted HQ PvP. You main damage output is Scather, if you can't cast waste every GCD on Scathe but do not dry out your MP.

Any competent team will target you first. If they don't it is your duty to punish them by blowing them up. (It is very easy as a BLM). Trying Bliz 2/1 into a 3 Stack UI then go Fire 3 rotate to keep it at AF3 or UI 3.