unity dash does not take input from several xkb keyboard layouts

I own lenovo z50 and recently installed 16.04 LTS. I use ubuntu in Hindi language. The following issue was also noticed in ubuntu 14.04LTS and later releases (although I did not file any bug for it).

Unity dash window (which comes after pressing Super key) does not take input from several keyboard layouts. "Indian" keyboard layout is used for Hindi language. When I type in unity dash to search for applications or files, it will not register any input whatsoever. However, it works fine when "English (US)" or "English (India)" keyboard layouts are selected.

"Indian" keyboard layout inputs fine in any other editor or wherever keyboard input is required.

I digged down further and found several language layouts face the same problem. These include "arabic", "armenian", "bangla", "georgian", "gujarati", "greek", "hebrew", "iraqi", "malayalam", "mongolian", "oriya", "punjabi (gurumukhi)", "tamil" and "telugu". Many of these are layouts for indian languages but few are not. This is not exhaustive list and I only checked few languages at hand.

These keyboard layouts come installed by default with standard ubuntu installation.

As many applications come renamed in Hindi, it is impossible to search them currently in Unity dash as it doesnt take Hindi input at all.

I tried to file bug via ubuntu-bug or apport-bug but did not succeed, hence filing a bug here. I would be happy to attach any other information required for this.

UPDATE : 27 Jun 2016
Backspace / Delete button removes multiple characters from editor in one stroke, instead of one. For example, for text in Devanagari script, सौरभ भारती, it would delete all characters in just 6 strokes, while it contains 9 characters and it should take 9 backspace/delete strokes to remove it. It looks like the swaras around consonants are taken as one character and its removed as a block in one stroke.