Sorry, but I don't think this helps swingyness much, because you are still getting a binary result: hit or miss. For the obvious example, imaging a hypothetical monster attack: +8 vs. AC 19; 4d8+12 damage. You need to roll an 11 or better to hit. Rolling 1d20, that's a 50% chance of hitting. Rolling 2d10, that's a 55% chance of hitting. So it's the equivalent of a +1, but the real take-away is that a single die roll stiil means the difference between 0 damage and 30 damage, which is kind of a lot. In fact, the expected value of the attack is 15 damage, but there's no way to actually ever get that result (since the minimum damage here is 16).One solution to this is to replace the d20 in the attack rolls of monsters with 2d10. Instant swingy buffer.
How has this been working out? How many APs do the players typically have? Do you allow multiple AP use per combat? Per round? Do you give the monsters extra AP to compensate for the player's extra AP?I've suggested this before in other threads. In my house rules, I allow using an action point to re-roll an attack as well as taking an extra action. This lets you hit more reliably with "big" powers, which goes a long way towards speeding up combat. I use the same rule for PCs and monsters.
I also hand out a few more action points than normal. That's been enough of a speed boost for me group.

(Dungeons & Dragons)
Rulebook featuring "high magic" options, including a host of new spells.