according to testing done, enmity does not decay
https://www.youtube.com/watch?v=bG8cmNLhUt8

the real question about keeping up with hate against a tank in same gear, was his tank pld and the other tank warrior? there is a noticeable difference right now, showing wars can pull hate off of plds, but wars also do strike harder

as for a healer taking hate off of a tank by spamming heals, that healer needs to learn to heal or people need to learn how to avoid unnecessary damage, and yes, overhealing DOES still give enimty