I’d assumed at first I must be misstaken, but I’ve now tested it through two games, and enemies are still able to cast spells immediately after being hit. Unsure what is causing this, so I’ll list the items and Helix choices I’m using in case it matters. The Helix is solely from the last match, since I missclicked on my level ten choice, but the bug was occuring over both regardless.
Gear: Bolstering Duelist Glove, Sketchy Gambler’s “Greyhound”, Antiquated Stout Aelfrin Warblade
Helix: Q, E, E, E, E, Q, E, E, Q, E