This has it’s pros and cons, but I just take Ageless Core without hesitation if I have to. This leaves me with small issues, like how my Shield/EM’s health bar moves a little more than yours, but it’s just a lot easier than worrying about endurance. Either that, or a lot of my proc monsters take Vigor Core. I’m just an aggressive/reckless player and only have Barrier/Rebirth/Clarion after end is clearly established as a non-issue.
Oh, and if I don’t have Ageless Core, I slot recovery powers more than most people because I can’t stand endurance problems. 2 Performance Shifter / 2 Power Transfer (+95.9% plus two procs) is normal for me for Stamina, Quick Recovery, Blaster sustains.
Though a large chunk of fliers would be Blasters who can handle their end just fine.