Razes kit is useful. i dont think its crazy strong or super weak. it's about space.
the B buddy is great becasue its essentially a scout that can do damage. maybe it takes off after someone and gets shot in the back. now you know 2 people are close and which direction they are coming. In lower tiers(where i am likely at 😃) it gives people a panic choice. follow it up with a shotty and the amount of people ive taken out who are looking at the ground shooting at BB is not insignificant.
the c4 pack is more about mobility. get yourself to high ground or bounce around a corner to gun an unsuspecting enemy down. it also does damage which is cool too.
Nade is solid it does good damage but again creates good space. the odd double or triple kill on stacked teams is hilarious as well.
her ult i use mostly as a peak follow up or initiation. fire at heaven from range and you buy yourself a few seconds to position assuming you dont get a kill.
in the end, if im raze and defending mid on the 'Split' map for example, i can delay a whole team long enough for flanks and rotations to take place. or conversely i can break that same spot by lobbing nades and BB buying space then moving in with a shotty.
i am aware that a lot of this is likely because, i am at best of average player skill. however, how effective each character is will differ from skill tiers