Jylpah, on 23 July 2020 - 03:31 PM, said:
I don't think "premiums have been nerfed several times". While WG EULA does not prevent WG from nerfing premiums, WG really does not want to do it since people ask for refunds, and can churn away or become more cautious on spending money. The game is flooded with OP premiums, and yet those are in practice never nerfed, but those get eventually nerfed by the performance creep (launching new OP tanks, buffing others to catch up). There can be cases when some premiums where "relatively" nerfed by not buffing them as much as other similar tanks receiving buff.
At least I cannot remember (but that does mean much) examples of direct premium nerfs. 
Correct, WG tries to avoid blatantly nerfing premiums to pacify their supporters, but it does happen more than you think.
For example, if they nerfed something like the 252u, people would be in an outrage. But if they gradually chip away at a tank like the Otsu, with a couple direct nerfs and massive powercreep, that is a better way of doing business.
For example, the infamous 5.5 update. Lost in the chaos is the small detail where the Kenny Otsu got a nerf. Devices/crew damage is not a huge deal, but it just shows that premiums are not invulnerable.
Another one is the E-75 TS. It received a side skirt nerf in 6.4, which arrived on October 16. You might say, oh it was still in testing, test tanks get nerfed all the time, and I do not remember exactly when it was first sold, but a simple Google search informed me that several YouTubers had posted In Shop videos about the tank on the 11th and 12th.
A similar incident occurred in 6.2, when the Vk 168.01 got its sideskirts thinned about a month after release.
I'm sure there are dozens of other examples, but these are ones that I had readily at hand.