Would you consider 50 games a starter workload?
In what world is Domingue a better choice than Darling? His best year in the NHL is significantly worse than Darling's worst year.
Korpisalo is closer, but there's still nothing to suggest that he is a better choice than Darling.
If your entire argument rests on "This player must have played a ****-ton of games in a row or he's not worth your time" then we should just keep Cam Ward. He's played mountains of games and has plenty of mediocre stats just like all the other guys you listed.
I would consider a playoff round a starter workload, 7 games in 2 weeks. Unfortunately Darling played that seldom. If you want to compare Darling's backup workload you need to compare him with other backup workloads either.
For example in 2015/16 Darling played 21 games with enough rest with .917 EVsave%. Pickard was .923 in games with enough rest, Korpisalo was .928, Domingue .934.
Do you understand that young goalies are still developing. Darling played NHL only the last 3 seasons when he was 26, 27 and 28 years old. Domingue and Pickard just had their 25th birthday, at 25 Darling played ECHL. Do you get this? You want to compare a further developed goalie with Korpisalo who is over 5 years younger.
Pickard, Korpisalo and Domingue are younger, played on worse teams than Darling and still were better at same usage.
Ward is a starter, but the idiots played him 8 times b2b and too much for long periods. I can run down every goalie too. CAR lost the playoffs because they overused Ward and were too cheap to get a better backup. Too cheap to claim McElhinney off waivers for free in January. And now they paid a 3rd for Darling's rights ... idiots. And the best is these idiots will pay Darling 3M more than Pickard and Domingue will make next season.