'Sup Don! About time I got to rating this team! Seeing some lesser-used mons is a nice change of pace! :)
As previously stated, changing Beartic's nature to Adamant
would allow you to OHKO'S after rocks are set up. Speaking of rocks, pairing up Beartic with a Rapid Spinner would keep some of the pressure off his shoulders and keep hazards from threatening your team. Volbeat would also benefit from a spinner due to its 4X weakness to Rock. For these reasons, I'd like to suggest replacing Mawile with defensive Armaldo
. Having a Rock-type on your team will lessen your weakness to Shedinja. Armaldo can also perform the job of setting up rocks.
I agree with WhiteDMist and Sweet Jesus' changes so its good that your testing them out.
Overall, this is a great team and I hope to see more like these in the future! Keep up the good work, man and Luvdisc'd! :D