I wasn't the biggest fan although I enjoyed his fights for the first half of his career. GSP was the only martial artist I would consider complete. He wasn't the absolute best in any area but he was so good at all core aspects of mma that more often than not that negated anything the opposition could do (ie his wrestling would knock their striking down a peg or two so he could overtake them).
Anderson Silva was good on the feet, in the clinch, and on the ground, but his wrestling was always horrible. Chael proved it in their first fight. (I'm speaking relative to the rest of high level ufc fighters and not joe average)
Fedor seemed pretty well rounded too, not as much as GSP but in his prime I would say he was up there, technically not as much but that might be more because of weight class and reliance on power and the lower the weight class you go that typically means you're having to use more things to stay out of trouble as your opponent is faster and has more stamina.
Most other successful MMA Fighters even at the highest levels have at least one glaring hole in their game, they were just good enough to ensure it never went there. For example if someone has horrible jiu jitsu their wrestling was so good they would hardly if ever be on their back against a high level jiu jitsu player.
In Mcgregors case I think it would be more beneficial to him to just work on either his wrestling or jiu jitsu, but it seems like he doesn't have a natural inclination towards jiu jitsu like he does boxing. I think it would benefit him greatly to hire an american wrestling coach. European MMA Fighters are mostly known for their poor wrestling ability. Judging from his frame he probably doesn't have as much raw physical strength has he has a tall range type body, he has power in his hands but that's different from what you would need to use to sprawl, however his sense of timing and distance in combination with footwork and his low stance he uses a lot would play really well into a sprawl and brawl style of fighting if he were to split up his camp and spend half his time at sgb and half at aka, greg jacksons, or somewhere similar. (I would also suggest team alpha male but clearly with his history with them that doesn't make it very likely hence why I left it out)
