Shouldn't Thyrus+1 be the last item I get when it comes to using Myth tomes?

[SeraviEdalborez]

does this work with other jobs? ie DRG?
becuase i took all of my gear off and had my Gae Bolg equipped with 44 dmg and +27 str --- after switching it with a lvl one spear with 5 dmg my strength went from 302 to 275 which is only subtracting the additional 27 str from my relic.

from my personal testing this theory is completely incorrect.

i would advise getting the gear that gives the best bonus stat upgrades

First, be aware that the damage boost from NQ relic to +1 relic varies:
+3: Mages/Healers
+2: All physical relics except...
+1: BRD

So the effects are a little less pronounced for BRD, so much that most advise getting it last. For all others, it's best to get +1 relic first.

Second, nobody said weapon damage directly adds TO your main stat. The boost it gives to your damage/healing is AS IF you had that much. Not the same thing.

[Luca_Brazi]

The boost it gives to your damage/healing is AS IF you had that much. Not the same thing.

ok thank you for clearing that up.
so if i +1 my relic (physical dmg +2) it would be as if i gained 18 str?

[Vactus]

ok thank you for clearing that up.
so if i +1 my relic (physical dmg +2) it would be as if i gained 18 str?

Yes.

Edit: WAR/PLD/BRD are the only classes that aren't required to +1 immediately.