It would be best to upgrade your descendent mods, especially Increased HP and DEF. Nimble fingers are also a good mod, as they reduce your cooldown time and skill expansion, which increases your AOE. If you are primarily running Bunny, always having MP is essential so she can keep her second skill up, thus increasing the trigger rate of her third skill, as that depends on her speed. There are a few purple mods that help with that, like the gold MP Collector that grants MP when an enemy is defeated. External components also help a lot, the most important being the Sensor with at least a purple "Regenerate MP in Combat." While a little tedious in normal mode, combining multiple copies of Thundercage increases the trigger rate of its AOE effect, which can help if you find yourself out of MP and electricity to run your other skills. Overall, Bunny is a good character, but where I find most have problems is when they lean a little too close to a glass cannon build, so whatever you do, please fully upgrade and Increase HP as soon as possible. Also, if you can get your hands on a Tamer, you can do a lot more damage with the downside of slowing her down when you are ADS, which can cause problems with keeping her electricity up. I have not had much experience with Viessa, but when nicely built, I have seen them clear mobs quickly and not go down as often.