Yeah they have a stupid amount of DLC available.
Each race for campaign has a set of war-gear available for the Commander. So if you aren't interested in playing the campaign at all then ignore it, otherwise its worth getting to get past some of the hassle with early levels when you get sod all drops.
Each Hero for Last Stand has a couple of war-gears available. Since Last Stand is probably where you'll get the most replayability its a good idea to get those. They give you alternative playstyle options that can be quite fun (and on some heroes, necessary early on to avoid sucking). The most entertaining (and totally overpowered) one is probably the Mekboys with his telefragging upgrade.
Theres a Tau Commander Hero available for Last Stand. As above, you'll want that if you play Last Stand.
Then theres a bunch of ridiculously overpriced 'skins' which you can safely ignore.
Personally I got the Tau Commander and All Wargear Bundle for £4.41. Ignore the Complete Character Pack.