In K'teng's Lab.

Went into the maelstrom and got aggroed by the lightning elemental. It cast a bolt at me as such:

A lightning quasi-elemental utters the words, 'diesilla barh'.
A lightning quasi-elemental thrusts its hand forward as a brilliant shaft of lightning lurches toward you.
A lightning quasi-elemental's lightning bolt MANGLES you!
A lightning quasi-elemental is in perfect health.

So I removed my mace and did an angelswing on it:

<711/873hp 724/724m 816/817mv 26000tnl|indoor|9 AM> angel
You block a lightning quasi-elemental's attack and sweep its arm aside. Quickly you deliver a powerful uppercut, leaving a lightning quasi-elemental spitting blood.
Your punch MUTILATES a lightning quasi-elemental!
A lightning quasi-elemental has a few scratches.

<711/873hp 724/724m 816/817mv 26000tnl|indoor|9 AM>
Your punch devastates a lightning quasi-elemental!
Your punch maims a lightning quasi-elemental!
You quickly strike a lightning quasi-elemental with the edge of a shield from the hide of a snow worm.
Your shield jab maims a lightning quasi-elemental!
A lightning quasi-elemental has a few scratches.

<711/873hp 724/724m 816/817mv 26000tnl|indoor|9 AM> angel

Your punch maims a lightning quasi-elemental!
Your shield blocks a lightning quasi-elemental's chaotic blast.
Your shield blocks a lightning quasi-elemental's chaotic blast.
Your shield blocks a lightning quasi-elemental's chaotic blast.
A lightning quasi-elemental has some small but disgusting cuts.

<711/873hp 724/724m 816/817mv 26000tnl|indoor|10 AM>
A lightning quasi-elemental thrusts its hand forward as a brilliant shaft of lightning lurches toward you.
A lightning quasi-elemental's lightning bolt MASSACRES you!
A lightning quasi-elemental has some small but disgusting cuts.

As you can see it wasn't able to say the words for the spell due to the angelswing effect, but the spell is still cast. Bug or by design?

Just like deafening a mob doesn't prevent them from casting, neither does angels wing