I'm not there yet either, but that's pretty much my expectation (and hope) as well. Even a 5% chance on regen tick gives a ~30% chance of getting at least one (likely only one) per regen, or a 65% chance over the course of a minute. Considering it only grants if you're in combat and don't 100% overheal like lilies (any 70s please correct me if I'm wrong, but I think I recall that from our other FC WHM), a bigger number like 10% isn't too scary. Around 50% per regen *if* none of them overheal. I feel it'd fill the supplemental-quick-boost-role a lot better, greatly boost its chance to actually stack to 2 or 3 on a target you expect to be taking damage, and ultimately would give you a reasonable chance to pop it once a minute which may allow you to save tetra for a bigger oopsie on another player that you don't have a failsafe for. It'd also help recuperate the time spent reapplying regens to tanks in two-tank scenarios by virtue of doubling chances at a stack, roughly.
Not to mention, y'know, HoT synergy.
As for Benison, I too am treating it like a free-ish tank heal every 30s or so, and it works alright as that. Doesn't feel good to see multiplie lilies go into it as the CD is short as it is, but not the end of the world. I've found it rather clunky to use when I'm actively trying to have a shield ready. It feels pretty weak right now and seems to disintegrate faster than stoneskin did....but that's probably just gear and leveling dungeons messing with my perception compared to running Exs at 60. Just having to train myself to remember to hit it at the moment. I definitely miss stoneskin giving me the option to babysit someone I feel can benefit from it, though. Rather than pre-shield them, gotta react to targeted actions quickly, and the necessity of a lily makes it not always practical to do so compared to adlo-reactions. I experienced this during an A-rank that many of us were 66-68 for, getting one shot by some of its targeted actions unless I had a benison available, but I understand that's not going to be a typical combat experience once we're 70.