hey nwa, just trying to help wasnt sure what your issue could be, but something doesnt make sence, even my bad r3 produce more vapor then a 510 atty while dripping, so in all honesty i have no clue as to why, thats why i asked if you tried a few, if they all arent giving you vapor then you must have a seriously bad batch. i have test vaped over 100 e2's and never had a issue where it doesnt give huge vapor.
ive had the dry issue, ive had the glue issue, ive had leaking, but not once have i had bad vapor prodcution. other then the ones you have maybe are to low ohm, i hate the 2.5 ohm e2 on a 3.2 or 3.7 but i love it on my variable. Then there is the ptb option but then its not a fill and vape, so far the r4 has been fill and vape.
the 2.5 ohm should be used at 3.0 volts unless you ptb it
now the 3.0 to 3.2 ohm e2 r4 work at 3.2 volts and 3.7 and 4.2 pretty well for me.
you could have a bad batch, thats also possible, many have recieved some .......s.
NWA, i know this is a dumb question but since your issue is a mystery ill ask, have you tried them with very tiny drags insteasd of longer drags.