Any tips for playing Ascendant on POTD? As I get higher in levels I'm struggling to max out my focus once in a battle
Get some good guns. My no. 1. recommendation is Kitchen Stove from the old city questline. Enchant it with Thunderous Report (1/per encounter) and aim the cone well (as enemies close to engage, but haven't arrived yet). This should typically lead to instant Ascension. Then get a Cleric to cast Salvation of Time on you.
A decent backup for a second Ascension is Amira's Wing rod from Amira's roost ruins on a south-western island. It casts horrid wilting or whats-it-called, unfortunately only once per rest.
Red Hand from Neketaka is a good general purpose backup. Target squishy enemies with it.