I know that the new MCPE 0.14 Beta 1 is very buggy, noticed that the Witch is not doing any damage at all because it is targeting/throwing the potions in the sky (very high) and does not hit you at all.

Steps to duplicate:

• spawn a witch
• hit her or stay close to her and she will begin to throw potions in the sky not being able to hit you

Update at build 6:
When between one and 3 blocks in front of a witch (but not in the same block as the witch) the witch's splash potions will never hit you. You can easily see this in 3rd person view.

To test, create a new creative flat world, give yourself some witch spawn eggs, convert to survival, change view to 3rd person (front or rear) and spawn a witch 1 block away from you. Watch the potions fly harmlessly over head. I'm as yet unclear if this can be reproduced in survival by running up to a naturally spawned witch.