Putting together all the arguments, here is my idea for a compromise. Keep the recast timers as is, but allow the CON to purchase traits with guild marks that increases the duration. The first by the original duration, the second by twice the first. That would bring prot and shell up to 20 minute recasts when cast by a CON. As long as they are CON only traits, that would make the CON a more desirable buffer, while at the same time relieving them of the burden of constantly buffing, and give them an opportunity to toss out a nuke here and there, because nukes are fun.

The way things are set up now, I don't think aura buffs are necessary, but I do think the durations are a bit short. I think part of the reason they have recast timers is so different CONs in a party can take on different roles. Although I believe those roles should be limited to "offensive" and "defensive". But at the same time, it should be possible to do it all, if that is how one wishes to play. What is the best balance? I can't answer that.