I don't think 3min cd instead of 4 will have a large impact on the overall performance of Champion dps. Keep in mind it's only a 15 seconds buff. As I've already written, if I should be wrong, an overperforming secondary class can always be adjusted.
Speaking of "nerf", I don't think classes that are already overcapped in burst or mdps that don't profit from cast speed see it that way. When R/Wd's buff was changed to a selfbuff no one batted an eye either.
I understand that you are upset since you got the iss for the sole purpose of supporting and I would be too, but high value investments were and still are a risk in the balancing process.
Sincerely, I play only support with Champion. I would appreciate it if the 104 ISS is still a group Buff or perhaps should be better a raid Buff in shieldform. Because Champion/druid is so such nice support, why should be forced to change the buff only as selfbuff?
Although I like the current version of the iss, I honestly do not care much wether the buff affects the group or just the caster. As I said, don't think it makes a huge difference in overall damage.
If devs were to change the status quo though, PLEASE keep the attack speed bonus for the caster. Fast autohits are important for Shock Overload.