It could have been infused with Ragain Atmas:
+5 TP/tick > Atma of the Sea Daughter
+3 TP/tick > Atma of the Sundering Slash
+2 TP/tick > Atma of the Voracious Violet
With these set he could have got 10 TP/tick per Hit, but the first Atma gives also a 13.3% Slow (at least seems so) so probably he just used a Monarch's Drink...