Hi Shazir! Thanks for the compliment on the guide. Personally, I don't think Cosmic drive is the best item to build on Volibear jungle. However, that doesn't mean that it shouldn't be built or that it is terrible. Volibear as a champion can pretty much build any item in the game and get away with it in certain games. My guide / main build is focused on giving you the best build for the mass majority of games that you play.

At the end of the day if you care more about having fun / just playing what you want to play then Cosmic Drive is fine to build. Keep dominating with the bear!

Trundle can be very hard to fight if you try to fight him after your combo. If he can stack up his Lethal Tempo or if you have abilities on Cooldown it can be somewhat annoying. However, if he isn't full HP you typically have enough burst to kill him with your Q>E>W Combo with Press The Attack. The longer the game goes on it gets much more difficult to fight him though.