Such amps are biased class A (probably for the street cred) and remember that you need to subtract screen current to know the actual plate figure. I find this especially important with the little bottles. In reality these amps are driven into AB due to excessive grid signal. This can indeed have them biased too hot for their operating conditions and I've changed a few myself. I guess you just have to take it on a case by case basis because there seems to be no end to this misunderstanding on the part of designers. Then again, El84's are cheap. 6V6's aren't prohibitively expensive. El84's just go microphonic prematurely. I don't know what 6V6's do because I haven't worked with them a lot. IMHE they pop actually
So, yes, I've noticed it too.