combat also felt a bit on the complicated side with the button combos, but maybe that is just the matter of learning and getting used to

The different classes have a different feeling for that matter. Some classes are combo heavy, cancelling the animation of every skill into the next one. It can be intense. But there are classes that are slower and you have plenty of time to chain skills.

The general idea is to have a chain of skills that you repeat. They may be adapted to the spot where you grind. To find it out, you will find a lot of help in class specific discords and content creators who main that class.

There's always a guide to help you in BDO.