It's probably for the best, though I do think it does make subtle nuances of balance a bit harder. Simplification isn't always dumbing down, but it's a fine line. Sometimes it's fun to count out your AP and calculate the exact moves and ability combos you can make, but it's also nice to just keep the combat moving, especially with 4 people. Just as the focus on two player co-op meant big design decisions in D:OS, an an effort to let 4 people play at once and all feel involved will mean making systems as uncomplicated as they can.
Crossbows could take an AP to reload. Two-handers could have a one or two AP basic attack option. I like the idea of the 2 AP basic attack being a cone attack that can hit multiple targets, but for less damage than the single attack.
They could also have more abilities that combo movement with an attack, like battering ram. An ability where you rush to within a couple meters of an ally. An ability like teleport but causes some of elemental explosion around the person you teleport. A two-pronged battering ram. More abilities like Nether Swap. Hard part is making the AI use these abilities well.
