I think it would contribute to bringing the early gameplay of AST and WHM closer into a line with eachother and it would serve to enable the "deal damage until necessary" playstyle early into a new player's career by not locking off access to an "oh shit"-button until Heavensward.
Ideally the Lv.15 version of Tetra should have a weaker potency (maybe 400, as the default potency of Essential Dignity) with an upgrade that boosts it to its original potency at Lv.60