Never ever heard of a properly tied and seated Uni knot slippign, cracking, buckling, splitting in my life - and am actually dumbfounded it's being questioned!
Crimping is pretty simple and straightforward skill to learn. I crimp anything over 250lb.
Roll knots are great, but you need to keep the loops small, tight and under hand pressure so that they don't spring out whilst making the knot. I use this knot when I don't want to use crimps but may want to join a bite leader to shock leader.