It basically yields the least dps increase per mytho than any other upgrades considering the relevance of DEX and the fact that the base damage increase is only of 1 point, which is half of what the +1 weapons usually add up.
So, if someone wants to maximize their dps during the way to a "fully best in slot set", +1 should probably be the last mytho piece a brd should get, doing otherwise is a sign of poor upgrade choices dps wise (hey, one could consider the glow a legit reason to upgrade perhaps).
Considering that nobody could possibly have gathered enough tomes for such ideal set even if they were legacy and benefited from the 2 mytho resets, a brd that currently has +1 is most likely a brd that didn't know better when they made that investment.