Hi brother @akdx
As far as I understand that it (Delwyn Dragonscale) can be use with any splinter, as it is a Dragon summoner. Its major buff is that it provides ONE magic attack and you have noticed that the Summoner that provides magic attack almost its ( Alric stormbringer) price is $173 for level 1. The different between these two summoner is that one have 3 Mana and second cost 5 Mana. 3 Mana summoner price is $173 dollar whereas 5 mana summoner price is just $12.44.
I don't think that its price is high rather than other summoner.. perhaps this is the reason that is why Delwyn Dragonscale is common summoner..😊😊
Have a nice weekend..