For Ranged Dps i would suggest about 30k HP unbuffed for RT (silver), 35k HP for gold, 40k for platinum (i think its called), and 50k for diamond
For Tanks, 50k on normal with 10k intervals between each difficulty
For Melee Dps, i suggest 35-40k HP for silver, 40k-45k gold, 45-50k plat, and 55k-60k diamond
Not an expert at Raksha's Temple silver+ myself but i still need to get a tiered lvl 65+ staff myself. (T4 +10 Aok Prayer FTW! xD)