Basically, either they make active regen such a necessary part of healing that you can not sustain your throughput without it or they make it completely optional. If they make it mandatory, you then probably would be forced to run with a lot more healers on progression heroic content than you would on normal modes. People won't want a system where a normal mode requires 5 healers and a heroic requires 10. The other alternative is to make every healer sustainable without a significant contribution from active regen. . In that case, you'll have enough passive regen to make do on heroic modes, but will also have so much available in easy content that you won't need to bother with/care about active regen.
I just don't see there being an easy solution. The Cata Telluric Currents and pre-4.3 Judgement/Seal of Insight model created huge balancing problems. That's probably why they are moving away from that.