Well unfortunately you can't often tell how good acid is by how many micrograms it is. The reason for this is the purity of the crystals that are used in the solution that was put on the sheet. while 300mcg of mediocre LSD may produce a good trip, 300mcg of needle point crystals will likely floor you for the peak. Not only this, but dealers, no matter how much they're "trusted" will often fudge the truth, if you're getting LSD with 200mcg of good crystal then congrats, because the majority of what I get is 150-200 ish and I've been in the game for a while, it seems to me (no offense) that you have not, therefore if you have a connect like that then you're pretty set. Most likely though, the blotters you're getting are less than 200mcg or possibly are 200mcg of not quite so pure crystal.
Now, with that being said my advise to you is this: when somebody tries to tell you how many micrograms are on a blotter, don't listen to a damn word they say, it's more than likely that they really have no idea, unless they're the maker, and if you're getting shit from a good producer then very much congrats to you. At any rate, talk to people who have done the acid before and ask them, not how good they were, but how many they needed to take to get the effects that they were looking for, of course also ask them how they like their trips, some people like them mild, I like to be floored.
As far as blotters being done unevenly... I'm sorry you have this issue but anyone who knows what they're doing is likely not going have this happen with their blotters.