It’s a situational talent. Artanis level 20 has always been a fairly weak row, with the old Force of Will being an exception.
Zealot Charge makes Artanis unkiteable and effectively means that the likes of Tracer and Li Ming isn’t playing HotS anymore. The main reason this isn’t a larger spike than you would think is because Artanis scales off heavily from level 21 and onwards due to damage levels being so high that Artanis gets killed during focus fire much easier than at any other point in the game.
It comes with it’s pros and cons. Artanis has very powerful talent rows especially inside his 13 - arguably the weakest talent row for the majority of heroes in the game with limited customization. Artanis level 16 is also a very powerful talent row so it makes sense that he has to lose some power in a different row.
Also I want to address your most recent reply - it’s not uncommon at all for talents to be very strong in certain situations and weak in others, that’s the whole point of picking your talents according to what you face.
If you face heavy mobility heroes pick Zealot Charge. If this isn’t an issue you’re free to take a Heroic Upgrade (Target Purified is one of the strongest snowball and “win more” talents in the game) and Plasma Burn is a decent talent into bulky melee teams and/or core rush DPS.
While I do agree that Zealot Charge is on the weaker side of Artanis available talents, primarily because it’s such a late talent. However I think it’s very unfair to say that it brings “nothing to the table” in the right situation.