Got to agree with Altimis here (who agrees with Pixelshader). In the short term, a lot of tanks favor getting a piece of AF2 over +1ing the sword because it does offer a bigger survivability boost. However, there's some things to consider longterm:

- With the exception of the Helmet, all other slots have an Allagan piece equivalent to AF2 that drops from turns 1-4 of coil. Even though the Allagan part might not be best in slot in a final gear loadout, the difference is so minimal between Allagan and AF2 stats that you should always snap up the allagan parts when you can if they drop.
- The sword will only be replaced when Turn 5 is downed... and even then the allagan sword will be a small sidegrade as it's not directly that much better.
- Right now, it might feel like you have "enough threat". But be warned. As you progress through coil, and groups start gearing up, every DPS player you play with will be getting more and more gear. Their relics will become Relic +1. Their gear will get more and more dps stats on it. YOUR gear however will mostly improve in the survivability stakes.

I +1'd my relic and I don't regret it. Aside from looking shiny, I know it'll be a "safe" use of myth tomes. The important thing with gearing up is to get as many meaningful upgrades as swiftly as possible, and the last thing I want to do is spend 3 weeks worth of tomes on an AF2 chest just to have Allagan Chest drop in Turn 1 the week after. And whilst I feel that right now the Relic +0 would be fine, I can tell that the DPS players I play with regularly are getting better and better, and I really value the noticeable threat lead that +1 gave me.

In a sense, higher threat can also lead to overall survivability in a weird way. When you're being really really chased by dps that are super close to your threat levels you're pretty much locked into spamming pure halone combo threat rotations just to keep ahead. When you have a sizeable threat lead, you have much more capacity for using utility spells. You can flash more on single targets for the blind debuff. You can weave in stuns on less-important attacks. You can conserve TP better with more shield swipes, or use shield swipes for the pacification where applicable. You can spend "downtime" casting Stoneskin rather than feeling you need to use it to get more of a threat lead. Yes you can do all that with any weapon, but the more threat you have, the more flexibility you have in what you do with your GCDs.