Is it worth sealing this chase?

[redhexagonal]

There is a plastic central heating pipe chased up the corner of the room, too shallow and has caused quite bad cracking in the past. It looks like the chase was filled with some grey material, not brown bonding. At the top and bottom it was only a couple of mm under the skim. The middle its probably 10mm or so under. I’ve tried to patch it up by raking out the cracks, sealing with Gardz, filling with easifill, applying mesh tape over the crack, then skimming with more easifill. Is it worth applying Gardz again to strengthen it a bit?

 

[blup]

Doubt it would make a difference other than appearance, what with the pipe buried that shallow and thermal movement from the heating and cooling of the pipe.

Blup