So I just had this problem creating an SSRS report to display different series whose value have a wide range. I started out trying to use scale breaks but ended up going with a logarithmic scale on the Y axis. This allowed the user to visually see high and low points. I never knew of this feature until I started with this report but now that I have found it I might go reevaluate some previous reports and see if this fits. But back to the problems.
The first problem was that when there was a 0 value the chart wouldn't connect the line graphs. It would simply skip that X coordinate for that series. The fix for this was fairly simple once I found it. You have to set the "Color" property for the chart series. Click on one of the data points in design view and look at the properties window. If the properties window isn't displayed, go to "View -> Properties Window". In that window find the "Data" section and the find "EmptyPoint" and expand that out. Go down to the "Color" property and choose a color. If you want to match the colors you are already using you will have to use the expression function and a switch statement. I.E. (=switch(Fields!Category.Value=1,"Blue",Fields!Category.Value=2,"Red",Fields!Category.Value=3,"Plum",Fields!Category.Value=4,"Lime",Fields!Category.Value=8,"Grey",Fields!Category.Value=0,"HotPink"))
This will connect the data point but they are still in the wrong place.
When I changed the scale to logarithmic, anytime there was a value of 0 for a given X the chart displayed it in the middle of the Y axis. It made the report look awful and inaccurate. I couldn't find any results with my google-fu, hence this post. I had to do a workaround which is kinda ugly. I incremented the data in my data set by 1 so it wouldn't return 0 but then set the series label properties to an expression that subtracted 1 from the results. It makes the line technically off by 1 for every event but you can't really notice it in this scale.
Hope this helps someone or myself if I have this problem in the future.