Skinner in no way "has to carry a heavy load" Pickard is more than adequate and could be getting more games. Its no excuse at all for Skinner to be seeing this many starts, and its a bad idea, but its something Skinner himself wants.
The 58-27 record is a team attribute. Many of those games the Oilers manage to outscore the flaws in goal. Its not like he's a game stealer, and rarely is. He's an average goalie as you say, The Oilers an elite club making do with average netminding, which just happens to be one of the most important spots in hockey. If not the most critical.
In anycase the only reason Skinner is a "starter" and Pickard a backup, or Campbell in AHL is the team went that way. even though both goalies had better stats here, regularly, than Skinner. it fell to Skinner, and remained with him. The concern that could be expressed is it hasn't been about who is the best option, its who was more ingrained with the coaching staff, and that of course was Skinner, due to Woodys connection with him, and in the AHL.
Had KK been the coach here the whole time or started the season here its even likely he would've gone Campbells direction and good possibility Campbell would have found his game. But KK is in the non ideal position of starting during season and so a lot of coaches in that position will just go with what the org is saying to run with. Never a surprise who Schwartz is saying to go with. Not that its crystal clear that it should be the case.
If you want further on Skinners record being more of a team artifact than look at Campbell last year being 21-9. Or Pickard this year being 9-4. These are very similar to Skinner records. they are the artifact of being a goalie on a good team. Some easy pickup like Korpisalo (just an example) could come in here and have a very good win percentage. just on the basis of the quality of the club.
Just to go one step further on that Campbells last two years in Toronto were 48-12. Can one REALLY go on those numbers. I'm not, ftr. But you shouldn't be either.