So I currently have my two set for the holy pally as well as several 378 items. We are on farm for 4/7 in firelands with the guild. I currently have around 800 valor and can buy the relic. Should I go ahead and purchase this in your opinion to boost my output for now, or wait until I have enough valor for the legs?
Well kinda depends. What legs are you using atm. Like if you have t11hc legs with 2 set you are in a too much hurry to get 3set. And they buffed pve item drop rate from BH. then i would go for relic but if you have like 359 tier legs and no 2 set or any other legs then i would wait.
relic is BiS, tier may sit in your bags as that heroic of piece you gained is beter than your normal version of the tier.
also legs you can get lucky with a drop from BH but relic the only place you can get it is valor.
Always, always get the biggest upgrades first. Even if you're not going to use your legs for example because your current ones are better until you acquire 4 piece, you still want to get the legs. A relic is such a small upgrade. My friend kept arguing with me about that on his Prot pally, and he bought the ring first simply because he had a 353 ring, instead of getting tier gear. Now he doesn't have 4 piece yet is wondering why.
Get whatever will be your biggest performance increase. Which will most likely be the biggest overall stat increase (relics aren't typically big on stats, so I'd wait)