The benefit of an 11 or 12-28 is it will give you a better low range but the larger spread comes at a cost - larger jumps between cogs. So it might just make your problems worse.

What cassette are you running now? What gears do you find yourself between?

I live in the rolling hills of northern NJ and I’ve found 2 things help -

1) figure out which cog you wish you had and buy another cassette and mix and match cogs until you have what you want. This’ll take a couple of shots - first time I tried this I ended up with a terrible result.

2) hope this doesn’t sound elitist (very much not that kind of guy) - being between gears like that points to maybe not enough “cadence tolerance”. Keep riding and mix in some low cadence days where you grind out on a smaller cog than normal, then spend a couple days here and there spinning a larger cog at higher cadence than normal. Eventually your legs will build a tolerance to the broader range.

Low cadence needs more leg strength (fast twitch muscle fibers) and high cadence recruits more cardio... might be the solution.