I also had a lot of problems finding usable software for drawing UML diagrams. In the end, I used UMLet, it worked sufficiently for my tiny class diagram and w

I also had a lot of problems finding usable software for drawing UML diagrams. In the end, I used UMLet, it worked sufficiently for my tiny class diagram and was easy to use and I could rearrange everything minutely as opposed to the underperforming auto-layouting done by PlantUML. I also tried around with StarUML but somehow it didn't stick. Time has been wasted in trying to recreate the same diagram in all these tools...