Spells being interrupted by healing

Platform: Windows
ISP: ATT Uverse
Type of Internet Connection: Wireless
Internet Connection Speed: 54Mbps
Date & Time: Many times in summer 2013
Frequency: Quite often
Character Name: Edyth
Race: HumeF
World: Quetzalcoaltl
Main Job: WHM Lv.99, DRK Lv. 99
Support Job: DNC, SAM
Area and Coordinates: Abyssea - Altepa, Sand Sweeper area
Party or Solo: Solo
NPC Name: None
Monster Name: Sand Sweeper
Steps:
1. Infuse Atma of the Savior, which allows you to occasionally be healed instead of damaged by attacks.
2. Fight Sand Sweepers, casting spells. Sometimes, midcast, the enemy will attack you (normal attack or TP attack, this glitch works for both), and you'll be healed instead of damaged. Sometimes, that healing will interrupt the spell being cast, despite the fact that there was no stun, knockback, or damage dealt. Because there is no other instance in the game where having your HP restored stops spellcasting, I assume this is a glitch.

So this is similiar to how the Creed set will occasionally convert dmg when hit to HP gained. I would have to say technically you are still gettin "hit" which is what interupts you not the damage so much (although if you have stoneskin and you take 0 dmg you dont get interupted.) I clicked this expecting to find someone casted Cure on you and interupted your casting.

Also its possible that its just lag in the chat log, many times i have finished the castin animation when in the log it says Trumpy is interupted.
Mob hits trumpy for 16 dmg.

Either way this is a odd issue, if maint ever ends I will try and notice if i ever get interupted when i get a Set proc on my creed armor. Then we can see if it applies to other Healed by dmg effects.