Charlotte is a Lightning element tank that can handle magic attacks quite well, and having thief as one of her sub jobs makes her quite distinct. Her passives and counter ability gives room for changes to either be a solid tank, or a more speed based unit. Her thief sub job also comes with Steal Time, which can be quite the game changer against certain quest/bosses.
Unfortunately, her defensive buff and hate generating skill is separated, potentially causing issues at times. Her EX job lvl 15 and 25 skills aren't impressive either, but EX 19 for Glorious Armor can make a huge difference.
Stats-wise, she is quite similar to Mont (King of Leonis) in many ways, essentially making her the magic tank counterpart to Mont with less damage, but is cheaper to build due to lower cost. However, Charlotte is much more capable at handling both physical and magic attacks, and possibly more consistent due to 100% DEF & SPR Debuff Resistance.
Wow she is so damn strong with those tanking skills, debuff and buff, resistances.. At first i think she is a magic focused tank, but i can see her taking some phys damage very well too. A sniper might be necessary againts her to remove buff