Looks like too much cotton as far as i can tell from the pic. It should move freely (but not be super loose, a litte friction is good) inside the coil and you'll want to thin the ends, so you don't choke up the juice wells. That said, you're probably vaping thinner juices than me, so the wicking might be just fine(i vape high VG, so not really typical for this tank). For me personally, rather than faffing about floofing cotton all day long, i floof a little, pancake the ends (so it's like a bow tie, the coil being the center, the wick being the bows), then trim the wick to make the ends like a spear tip (so it thins out from the center). If the cotton is burning out in the center quickly or you're getting harsh hits early into the build that's usually a sign of too much wick and spitting (for me at least) is normally too little wick and/or not enough watts (because the juices is bubbling on the coil and not fully vaporizing - although that can happen if the deck is flooding to).... YMMV.
I build my coils 3-4mm ID (current is 4mm), it all comes down to the wicking tbh.
My builds usually look like John's after a while (often worse, if it still vapes i usually keep going until it becomes unbearably bad).