Gloves as the primary way to save off cold fingers when the temp drops below about 30 degrees is always a losing battle IME. You start using more wind-blocking and more insulation, which causes more sweating of your hand and fingers and there is no balance point. If you had enough airflow to keep them from sweating, you'd have super-chilled fingers from wind-chill. Riding with insulated gloves becomes like trying to ride with boxing gloves, no or very poor bike control, and your exertion level just varies too much. Some of the best results I've had are bringing some extra dry gloves or mittens. I have some soft-shell mittens I bought too large on purpose and they allow me to change gears and operate my brakes, keeping my fingers on the bar. This keeps my fingers together and warm. They still get a little clammy so they are what I go to if my normal gloves start to get chilly, but from that point I will do things like stuff the other pair of gloves down my shift or in an inside jacket pocket to "warm them up" with my body temp for 20 or 30 minutes. Then they are at least warmed.
The other thing is foot-warmers, they are adhesive and you can grip these to the bar, depending on your grip material, they'll stick by themselves after a while. These are a nice way to give you some heat.
I use pogies in the winter, generally on my fatbikes, but I do use them occasionally on my mountain bikes when the trails are clear enough to ride. The advantage to pogies is you can run a much thinner glove, giving you much better control AND better moisture management. The Dogwood Designs pogies can be rolled up to get out of the way so if your hands are getting too warm or starting to sweat you can address it.
That temp range can be tough, because some people can be "just fine" with normal gloves, and others can have frozen fingers that don't get any bloodflow, at that point it might as well be -25 instead of +25. A glove that "works" for a temperature range is only as good as the blood-flow in the fingers that it's going to protect. YMMV.