Efficiency 5 with haste 2 beacon should be able to mine deepslate.

Personally, I think that you should be able to insta-mine deepslate with a netherite pickaxe enchanted with efficiency 5 and a haste 2 beacon. The moss-mining technic is way slower and consumes more time and resources (bonemeal) than insta-mining. Furthermore, it gives you a lot of moss blocks and similar stuff, but the quantity is just too, whereas with instamining you can get lots of stone blocks (deepslate in this case). Stone is way more usefull in the quantity you get from insta-mining than from moss-mining. One possible solution is to increase the power of the haste 2 effect. This preserves all block durabilities and makes live easier. It's time consuming to get a beacon, so it should be more rewarding for the player.