Issue? I don't see what the issue is.
St Vicious can win with Karthus jungle in the expansion tournament. Unicorns of Love can win with Twisted Fate jungle at IEM San Jose.
Is that an "issue"?
Hell no! Those guys are renowned for making the jungle benefit their team.
There are HUGE tradeoffs to picking an ADC jungle.
Primarily, early clears take longer, are more vulnerable to enemies, and require kiting.
On top of that, most team comps rely on the jungler for map control, making picks, and engaging teamfights. Those are things most ADCs don't do well. Warding/clearing wards is dangerous for ADCs. If you can make playing an ADC in the jungle worth it, then well done.
Oh, and good luck dueling that Lee Sin, Kha'Zix, Rengar, etc. from lvl 2-16 that can dump on just about any ADC until they get a few items under their belt.