Pokemon DLC's are so weirdly implemented you're fighting generally weak pokemon inflated to higher levels making it odd to use your previous team as they will be too strong but at the same time difficult to start building a new team because the level disparity across the zones is really high so either everything is a breeze or you have to grind out a new team which feels awkward. I know this is a long rant but I honestly think they should just use lower level pokemon in the DLC and treat them like a reset because as they are now they just feel odd