Horrible battery drain when screen on only (5.1)

Hi, running latest firmware + 2.10.410.1 roms, tried Maximus and ARHD, both with prior wiping, dalvik/cache wipe, battery cycle etc. When i am actually using the phone it still gets quite warm plus i can literally watch my battery percentage drop 1% every two minutes just using whatsapp. Happens even when not installing anything except whatsapp, gmail etc. I tried battery monitor, but it simply shows those apps (whatsapp) etc, not really WHY they are draining so much power when in use. Standby time is perfectly fine....

Anyone else notice such issues? Anything i can do to test further?