I have recently discovered the joys of epic! As mainly a solo player, it irked me that I wasn't using some of the cards in Siege of Annuminas when I played it in standard mode. Of the 60 cards, only 35 are in the encounter deck, so with proxies (or you could use 3 x the product), I set up a 3 x 2-handed game. It gave a good experience all round - the epic version of SoA is a great scenario, thoroughly to be recommended. It also stretched my card pool, as I was aiming to keep uniqueness to a minimum, and caused me to dust off rarely used cards.

Followed that up with an epic duet of the Black Gate Opens and Mount Doom for the end of my solo saga. Again, brings in unused cards, a different experience on these quests, and if you haven't considered it before, I recommend you have a look!

Do you need two copies or more of siege in order to play epic?

To play epic mode for Siege of Annuminas you need 3 copies of the scenario pack, or go the proxy route. Same for Attack on Dol Guldur, although the latter scenario would need more proxy cards, I recall. No extras needed for BGO / Mt Doom.

I just played standard difficulty with my sister back in March. It was devastatingly difficult. But the victory was very sweet.

I am pondering whether I ought to order two more copies and try it two handed, else that might be a lot of proxying.

I finally got round to buying my third core set, so have plenty of spare encounter cards. I sleeve my cards, so proxying is viable, but as you say, a lot of effort. If I look to play epic Attack on Dol Guldur, I would look to buying at least a second scenario pack, if not all three, as the deck count is higher for that quest.