With the recent posts regarding battery's I would suggest getting a load test done on your battery to start. Might be w/the extra draw of the heated gear the charging system can't maintain, keep the battery charged. 

Ride Safe,
Fired00d

Can't know yet where the deficiency might be. Even before yanking the battery would be worth checking that all the cable ends are tight.
Strictly in the "for what it's worth" department the gear described shouldn't outdo the output of the charging system. Before I got my Gerbing stuff years ago I checked the power requirements of the gear and one full set of jacket liner, gloves, pants and socks were ok even running on the output of an 05. The 06 and newer bikes have a charging system with more output than the did 05. So relative to the gear described the bike should have kept up.
If the bike did not, and if it's not as simple as a cable problem, yeap, something is obviously a problem. Battery or something. But it'll have to be diagnosed and discovered.
Longest day I ever did with the heated gear on continuously was from Maggie Valley back to Joplin, MO one trip. That's about a 750 mile day and one of those trips several years ago was such the gear was on all day long. I didn't have the socks on but had everything else. With everything on and the headlight on high beam I could see tell-tales of the system not quite keeping up. Running without the spot lights or with the headlight on low beam and it was all good. I think that was when HIDs were installed; maybe still the halogens. Just not sure. With an LED later that might have been enough to make a difference.
You can't really trust your volt gauge to give you adequate information to know what you're wanting all the time in a case like this. Mother Harley won't spring to give us more informative amp gauges though. So sometimes we're left (literally) in the dark.