I feel that Promathia was the more epic battle but I still do love the Shadowlord battle. Even after doing it 5 or 6 times it still gets my blood pumping. The music is phenominal. I've done Promathia 2 or 3 times now. I have to admit it's badass. My first group didn't realize you needed to kite Promathia during his second form and got decimated and only left a few of us half alive so we basically were PLing Prishe through Promathia until our melees were ready to go and they finished off his last bits.

It's honestly more exciting to have Selh'teus 2hr during that battle than anything else. Everyone gets painfully low and Promathia is raping you with AoE that can't miss and Silencega that can't be removed with Echo Drops... Then Selh,teus busts out and everyone is totally full with 300 TP and you are totally saved.

I guess I'd have to go with Promathia because he's still hard. Me and my wife can duo the Shadowlord now so there's never a worry of dying which does take away a bit of the epicism.