To be fair, most maps are not really risky with Maribel. A lot of the time the stronger enemies come in waves so you can just use her skill, kill the dangerous wave, wait for her skill to be up again and then use it on the next dangerous wave. I did this a lot in the past. Heck i used to have Maribel + Bernice and not even level Leanne. Maribel filled in any hole i ever needed an offtank for while Bernice held off the main area. Nowadays that's Deine + Bernice though.