is there some rule against using goad?

[Korilynn]

Not really. Goad slowly restores tp, it's not an instant refresh like invigorate. If you would see tp bars and use it once you see someone get's short on tp, it's almost too late. Goad is more about preventing to even get too low, or to prevent someone from having to use invigorate, so it's more about 'knowing' when to use it rather than 'seeing' it.

For other stuff like dungeons, i just give it to the tank whenever it's up, especially if it's a war.

I didn't realize it was a refresher, and not a instant boost like Invigorate. However, I did start just giving it to the WAR/MDR tanks, as I recall with my MDR Overpower could drain me, so I did make them a priority with it.