Shemira is still an excellent choice for the early game, but you should make sure to stop once she's ascended. I think OP and many others look at the game too much from their perspective of being at the Endgame for over a year and having access to all heroes. As a newer player, at least for your first six months of playing, Shemira is the easiest hard-carry to build and will 100% be your most valuable unit for Campaign and Labyrinth.

Imo this boost in the early game is absolutely worth sacrificing a few copies of "meta-endgame" heroes for, since you will hit important campaign thresholds much earlier and can clear stuff like Twisted Valley, Abyssal Expedition etc that much quicker.

Imo newer players should be VERY careful when listening to the advice of endgame players or whales since they can't relate anymore to the early game. I would be very interested in two accounts starting out and one focusing on this guide and the other focusing on Shemira first and would bet good money that after a year of playing, the Shemira account would be decently ahead.