How good is XIMB BM for a person with following academics, 10th-95, 12-92.8, and BE (2017)-85, and with work experience of 6 months till April? Should one join it at this stage?

With such good scores, no one would suggest you join XIMB though it is a pretty good college and reputed too. You should give a shot to old IIMs. 

To get into old IIMs, you must score at least 99+ in the CAT exam, but if you have a score of 95+ also, you will land up in one of the new IIMs. Apart from the IIMs, there are other B-schools as well which are pretty demanding and rank high in MHRD ranking such as SP Jain Institute of Management, MDI Gurugram, etc. These institutes are also in the same league as old IIMs. 

In a nutshell, you should continue with your job and give the CAT exam to score the 99+ percentile. You will be able to get a better college than XIMB. If you are capable of getting something better, why settle for anything normal. Just re-think upon it and have faith in yourself.