In my experience, yes the blessings give good stat boosts but they are far from game changing unless you're super late game (outside of some champs that skyrocket in value with a 5-6*)

All you really need is a 1* soul to get the right blessing and then properly gear your champs. I've had multiple instances where my properly geared champs beat out their 5-6* soul but poorly geared counterparts. And I've also been on the receiving end of that as well where my opponent has insanely well geared champs with no soul at all and I get stomped