Sort of. Fewer frames per second means fewer characters are shown per second. DT is simply the time it took to complete the previous tick. To keep the effect at a constant speed (or as close to constant as possible), you'll need to modify the effect to take dt into account.
Take a look at this: [attachment=0:2nd0gu5f][/attachment:2nd0gu5f]
Thanks for the example file. It looks like I'll have to rework my dialogue system in order to get it like this. Ah well, on to work I guess!