Because I trust my biners way more than I trust a sling threaded though bolts, I consider a relying on (my) single biner safer than the above set up. 

With the hardware visible to me in that picture I would make a single point anchor using two biners, sling and one bolt, and back it up with the sling though the other bolt providing redundancy. 

Effectively close to what you did but one of the biners  moved off sling to the bolt hanger and add a stopper knot. 

The system has no cross loaded biners, is redundant (except for the single screw gate biner  on the rope end ) and does not rely on slings threaded though bolts.