If you look at my data above, with AF inactive (I use back button activation) the lens use 80 mA vs 309 mA for the body only during 30s exposure with my 12-24mm. That is about 26% increase in power consumption. I do not think e-aperture matters much - my 300PF actually has lower power consumption. It is hard to say how a third party lens matches up without any empirical data though. But likely the electronics in an advanced lens has to stay on as long as the camera, not only during AF operation. It all adds up, but it is not a factor of two.
It could be interesting to see what it comes out to if you repeat your previous test with the same AIS lens, battery and settings at the problematic high ISO.