See, you said it was useless back then, it never was useless. And iirc we would most of the time take the E-100 over the maus anyday, i haven't seen a maus get taken into a clan wars battle unless we were facing a shit clan.
The E-100's armor isn't much worse than the Maus is, it's also a bit more mobile, while also having a gun that does double the damage.
tier 10 tanks are for noobs