Bert
Most of the problems with the AIS site stem from a lack of proper understanding of how it works, or indeed how the ICAO NOTAM system works. I speak as the AOPA representative on NOTAM matters and have had an unhealthily close association with them over the past few years.
Plotting NOTAM is a tricky job. ICAO requires that each NOTAM has a geographic centre and a Radius of Influence (RoI). Something affecting an entire FIR will therefore have a centre roughly in the middle of the FIR but its RoI will mean that the boundary, were you to try and plot it, was off of your chart so how do you plot it? Plotting works fine for things that cover a limited geographic area but has limitations when it comes to big stuff.
For the AIS Site:-
First off, make sure you use a Narrow Route Brief (NRB), not a Route Brief. The Route Brief gives you aerodrome NOTAM for your departure arrival and alternate a/d plus the ENTIRE FIR. The Narrow Route Brief by default gives you NOTAM affecting 10nm either side of your intended track and does not result in a forest being felled. You can further filter down the data by using the filtering tools on the site, for example changing the Traffic field to VFR instead of the default IFR/VFR and by changing the UTC Validity Period (if left blank you get NOTAM valid during a 48 hour period starting from when you press Submit).
If you want to cover a geographic area rather than a route (for example for a multi-sector route or a circular X/C try this technique:-
Look at your chart and find two a/d that straddle the area in which you intend to fly. Use the NRB and set these two a/d as the departure and arrival a/d. Adjust the "Narrow Route Width" to create a box either side of the line beweeen the two a/d sufficiently wide to cover you intended area of operations. Put the a/d you intend to use during the flight(s) in as alternates to make sure you get any a/d NOTAM affecting them.
I'll be happy to respond to any technical queries you might have.
Mike