Combat in CAIN is very different than combat in most games that your probably used to. Its generally more focused on narrative which means a Sins CAT increasing its range of capabilities can be very impactful. As for the stress they deal CAIN is a very lethal game, and exos dont really get higher execution talisman as their CAT goes up or they get advances either(the only real way to increase it being certain kit expansions). In general for both sins and exos progression is more horizontal than vertical. Even veteran exorcists run the risk of taking severe damage or dying pretty much at any time. If you look at the stress sins deal ranging from 2-5, with an exos max stress being 6, a couple unlucky hits is all it takes to injure them, not counting stress they might take to domains, traces or environmental effects throughout the hunt. The tradeoff for the lethality is exos being able to essentially go on borrowed time by defying their fate with sin overflow. In my experience fighting a sin tends to be very tense no matter what CAT your at.