Not really. It makes sense since distributing interlocking skill interactions encourages players to craft new builds. Although Wiz3 has no real reason to have Quickcast, it imposes opportunity costs that are neither too steep or too convenient. I’ll get to the latter one later.
For the first point, imagine getting Quckcast as a Rune Caster. Not only would you be getting QC at R6. but you’ll also have to spend time or silver to unlock it–an example of an extremely steep opportunity cost. Consider Thauma, for example.Thauma increases M.Atk and gives Quickcast without having any damage skills to it. Thauma doesn’t need Quickcast (fr. Swell Brain) nor can it take advantage of the bonus M.Atk it receives since it has no damage skills. Wiz3 is perfect since Ele can only be acquired at R4 and farming out QC allows the Ele to spend its points more meaningfully. Thau 3 is perfect since the entire class is usually taken as a damage supplement for later classes such as Shadow, Onmy and the RC-based support builds especially since Thau needs no gimmicks to transfer its buffs to anyone and it happens to be the best support a Wizard could ask for.
This what we would call synergy. It’s a condition that arises from a game’s balance that encourages diversity. There are, of course, two types of synergy: a positive and a negative one. The positive one arises when there are explicit or implied interactions between any group of effects. The best example of this would be the Quickcast benefitting RC, Ele, and Onmy. The negative one is caused when the lack of a necessary component forces players to explore outside a known comfort zone. The best example of this would be the Shadowmancer ground-only attributes. What this does is force players to tinker with builds to find an appropriate and satisfying combination of classes. Now, suppose Ele or Omny had innate Quickcast. There would be very little reason for people to pick any other classes other than these two (Except maybe Onmy since the class benefits a lot from Thaum).
TL;DR: I just woke up and I don’t think I made any sense
That said, I miss the days when Wiz3 had a bonus 50% to magic damage.