I'm going 3oC as I got two exotics from them last night that dropped at 318 and 320, I was sat at 315 at the time.

I got my warlock fairly high then leveled FWC 8-9 times and was able to get gear to infuse into my other 2. Then when they ran the raid they got higher gear. Now all 3 of my guardians can be over 330. So I would suggest doing the same. Get one guy as high as you can get them then use heavy synths to faction lvl him as much as you can to get gear for the other 2.

Exotic engrams have the added affect of dropping above your light level, so if you want to increase your light, that's a good way.