However, the data editor is really horrendous to use, people should avoid using that unless necessary! Probably way more can be done if there's an active modder community.
Horrendous? No, unless you're doing advanced actor work (I avoid that for a very good reason). Slow as hell? Absolutely.
Once you understand the principles behind how the Data Editor works, it becomes fairly straightforward. You just need to understand the numerous steps involved in creating abilities. For a more complex ability, you will most likely find yourself moving back and forth between the Behaviors, Effects, and Abilities tabs making stuff constantly. It is possible to understand, however, and with a proper investment of time and patience you can potentially do almost anything. If you discount victory conditions and selectable factions (the kind of thing that actually lets you pick, say, Gondor or Mordor or Eriador in a map about the War of the Ring, since Blizzard in their idiocy failed to include this by default), you could make an entire map without a single trigger involved.
Back to the custom mapping community: There are some really good creations, you just have to know where to look. Admittedly, this can be a difficult task, since there is still the usual flood of mediocre maps to sift through. I'll try listing off a few maps right here:
Smashcraft (3v3 hero arena) - A fun game, very well-made, lacking in any real bugs. It comes with a selection of 5 heroes in each of 4 categories. Four maps are available as options, and it comes complete with a Rematch option when one team wins the best of 5 battle. There is also another map, Smashcraft Legacy, that has another four maps included for a grand total of eight arenas.
StarWars Assault (3v3 or 5v5 battle with fighters, complete with custom models and icons) - This is fairly straightforward. You pick a side (Rebels or Imperials), pick a fighter (5 choices per side), pick some abilities and passive skills, and then fight for five rounds (you are allowed to repick your fighter after every round). Each team starts with a certain amount of points, and points are lost by the loss of fighters (fighters have a cost value).
Heaven Besieged (Siege map, picture something like Helm's Deep) - A fairly straightforward siege map, much like the Heaven's Last Stand maps from SC1.
Siege of Nox Castle (Siege map, this one made by me) - A map based on one of the Fire Emblem games, with upgrades that can be purchased by killing enemy heroes. It also includes some flying units.
There is also the LotR-ish community (the chat channel is "lotr"), with over a dozen maps, for those that care for that gameplay style. The community currently consists of around thirty to forty members, so games can go up fairly often (the majority of maps are seven or eight players, with the extremes at five and ten).
