when you are level 90+ you can get much shining dust in the dungeon (Tears Marsh). even more when you're lvl 100, i think mobs in AR drop mush of them.
for T5 scrolls and pots materials it's the same case for basic material as for stones.
but for T4 herbs/mushroom/toadstool , yes it's pain, best thing to do now is to farm T3 and comp them to T4, still pain
i've already started making T5 HP pots, for T5 scrolls, i don't have all the recipes yet, i'll farm them in DT after i hit lvl 95, for some reason you may know
edit: answer for HG question:
No, when both are +0
maybe, when both are +9 (no one can make +9 T5 weapons yet, no perfect eyes/miles in OS store)