Ideally, you will have Dignity available for immediate recovery from the tankbuster. If you don't, precast Benefic/II.
Collective Unconcious is an instant oGCD action that applies a 750 total AoE regen in less than a second (committing most oGCD actions locks you for 0.7s). You don't have to stand there playing Titanic. As soon as you press the button, everyone gets a 750 regen. It also refreshes the duration every time it ticks while you're holding it, so every three seconds that people stand inside it adds another 150. But really, you don't have to hold it for the duration. You can activate it for the regen and then instantly start casting something else. Additionally, applying Celestial Opposition any time before it expires adds another 3-4 ticks, or 450-600 potency per target. So at the cost of 0 seconds / 0 GCDs, you can apply a 1200-1350 potency regen on the entire party.
Not that enmity is a solid indication of anything, but if I were basing it purely on enmity, I would actually buff the people who are higher up. It's not your job to prevent people from out-aggroing the tank. Give it to the person who will get the most benefit from it, and let them and the tank worry about who's tanking.
In a light party duty, use your Ewers and Spires. In light parties, don't Road your Spires and Ewers during combat because then you will be spending two draws on less than 200% effect, since AoE 50% on four people is not as effective as 100% on the best target twice. In particular, don't Road a Spire or Ewer unless you are already holding a Balance/Spear to use with it. Roading a Spire or Ewer without a Balance/Spear to use with it reduces the value of your next Draw.
Still in light party, your best Road card in the middle of combat will be Arrow, because 200% duration with 100% effect is still 200% effect per two draws. Roading a Bole gives only 150% per two draws, and Roading a Spire/Ewer gives less than 200% effect per two draws. However, if you're between combats, the opportunity cost of Roading a Bole, Spire, or Ewer is less, so the net benefit is greater.
In full parties, burn all the Spires and Ewers. All the AoEs, all the splodies.