Nostalrius Begins - Quality wow vanilla realm (1.12)

Is this vanillalike?

A Caster class starts casting a 2-3 sec spell on rogue. Rogue stealths, the cast is not broken it keeps casting then hits and breaks rogue out of stealth.
This has happened to me on multiple occasions even against lower level enemies that are far away, no way in hell did they not break target.
This scenario does not happen on vanish though.

Doesn't seem too consequent, if this problem don't appear while using vanish.

Very gamebreaking issue, should be fixed as soon as possible.