Had a feeling it would be. That's why I chose cleric for my faith build over knight - worst case scenario the stat is useful and I've got some catching up to do, best case I have less points wasted in a pointless stat.
I'm not going to echo the sentiment that adaptability is as useless as resistance, but my soul levels are precious, dammit!
I am pretty sure agility, not adaptability, is the valuable stat, and it's raised by ADP and ATN. I am pretty sure it makes you drink estus / use items faster and makes you more quickly recover from rolling. If I end up with 2 soul vessels again, I can drop by adp from 32 back down to 6 and see if I'm imaging it, but while it doesn't add i-frames, it does feel like it makes a big difference in more subtle ways.