I'm pretty sure he mixed right... by diluting I think what he's referring to is diluting it first and THEN adding it in... hence his question about why it would matter... for example, some flavors are very thick so i've heard of some people who dilute it in pg (or PGA) first and then add it to their mix...
But if that's what he's asking, and I'm pretty sure it is, then no, there is no reason to do so with your nic... 10% nic is already diluted... It's only 10% nic... LOL... No reason to dilute it before adding it...
Now as for the original question... My first thought is steeping... Any juice when I first make it typically has a "harshness" to it... I can't really explain it... But after a good hot water bath, a day with the lid off, and then about a 2 week sit, it mellows out and becomes a beautiful thing. It's my believe that the nicotine molecules dance with the flavorings, make sweet love to them, have babies (gestation period for flavorings and nic is very fast) and the end result is the steeped juice...
Ok, maybe not... but seriously... You'd be amazed what even a week of steeping will do with a fresh juice... let alone 2 weeks or a month... and different flavorings tend to be different... some can be pretty usable right out of the beaker... while others take several weeks to come into their own... As for the 24mg? Maybe it's just because 24mg is kinda "harsh" to begin with... someone who is used to 24mg is probably pretty accustomed to that harsh throat hit... so what they get from the unsteeped juice might not be that unusual to them... whereas someone used to 6mg is going to notice it a lot more? I dunno... just a thought...