truenaming is just simply to hard...
first of all the cr doesnt scale well with your char level...
15+2*cr as a dc is just way to much.
you will not make the check against any monsters especially those who are at the end of your quest.
second each time you use your utterance the dc will incresae by 2(law of resistance)
which is just
quickening a utterance ist even more stupid... increases the dc by 20
ok lets think about it...
you should be able to get a check of about 40 in the higher levels 23(ranks) 10(item) maybe high ability score
but the check you have to beat is: 15+2*20=55 without any modifiers
throw in spell resitance of monster bypassing that adds another 5
so were at 60
as a examle: already used the word of nutrition utterance to heal your buddies/damage the baddies couple of times?
make that 70+
its that simple you cant expect to be doing well...
if you do not throw in tons of cheese,
like a +30 item
item familiar for another +23
and other stuff
it will not work
and even then you cant use your abilities all time because law of resistence will push the dc out of reach sooner or later
but anyways the book had only two really good features... BINDERS and DARK CREATURE template