On Tier 1 Regeneration Master has the least impact in a lot of matches of all the skills in that tier next to Righteous Smash. You would get much more benefit from Reinforce, since it is mitigating damage versus restoring health, outside of combat. If you have 4 seconds to waste to trigger regens then you should have hearthed/ran back and gotten much more health back in less time.

As for Imposing Presence if you get attack during a team fight that reduced ATK SPD on heroes who rely ; Nova, Illidan, Zeratul, Falstad, Tychus, or Valla, can by the turning tide for you team since they would have an estimated 15-50% DPS loss (depending on the hero) from hitting you just once.

I myself used to use the shield heal since it is approx 7% heal per hero hit but that is also dependent on my own survivability plus enemy positioning.

Mind you these are from my experience and opinion, but the health regen is only OUT OF COMBAT, so some food for thought.