Every multiplayer game in active development receives balance updates. Metas shift no matter what. The fact that the game still receives balance updates in early access, does not prove that the class system doesn't work.
You are right. But the fact that the factions
did not get any more balanced itself throughout all the "balance patches" in the last two years has proven that
TW is not capable of balancing the class system they created!
The "balancing" resolved 90% around skirmish only, yet there are always factions above 60% and below 40% WR... in Skirmish!! Everything outside of 45%-55% is a big fail. I dont even have to start talking about Captain and Siege balancing

Good luck balancing all the prices and perks for Skirmish, Captain, Siege and Battle. Im 100% confident you will never succeed based on last two years
Also the notion that an equipment based system would suddenly solve all balance problems is kinda ridiculous imo. I am not saying that the class system is superior in every way with that btw, before that argument starts again. There are definitely benefits to it and I love warbands equipment based system.
I agree, the only reason why the equipment based system was so easy to balance is because the factions were so similar and had similar access to similar items. The biggest upside of the class system is that every faction actually feels very different to play.
Anyway, classes will stick around for Battle mode, but class costs will be different from skirmish and casual (tdm/siege). Same goes for some perks that will be different in Battle mode.
Also the economy (gold gain parameters) of battle mode will change with 1.7.2 (in addition to the troop cost changes).
Class system does not make any sense in battle mode, especially if the difference between the troops is day and night. One round you spawn as high equipped raidboss... next round as retarded peasant. If the strengt of troops aswell as the cost were close together maybe it could work, but you cant change that because the peasants are needed for Skirmish. Weak peasants shouldnt even exist in a single life mode. And the gold gain should not be that dependend on kills, because sending already bad players 60% of the time on a peasant must be a horriffic experience for them.