What kinds of people do you game with? Are they the kind of guys who like to win every battle, or are they willing to give anything a try once or twice?
I ask, because, in a jungle, you will have a decisive edge. On the normal, nearly barren tables, that so many people use, you will be severely handicapped. Make sure that a couple of your friends will be willing to fight on a jungle table once in awhile, and make sure that there is actually three or four areas of "jungle" on all normal game tables so you get some use out of your infiltrators and ambushers. If your tactics are good, you can succeed in a normal battle with just a few areas of vegetation. I have a cousin who does just that with his junglefighters.
Advice? I have fought against them, and alongside them, but I have never commanded them. I would take a couple of solid infantry platoons. Arm some squads for close in work (meltagun/heavy flamer), and some for ranged work (plasmagun/missile launcher). Arm your ambush teams for close in/anti infantry work or for close in/anti tank work. Have a couple of teams kitted out for each of these roles, and run the teams in tandem so every squad has support nearby.
Deathworlders are a "close in fighting" type army. Specialize in that role. Use lots of flamers. With your enhanced Weapon Skill, your men will do better than the average guard in close combat. The ability to field platoon leaders who can hold their own in HTh is also helpful. Don't be afraid to get close!
Conversely, you will lack long range firepower. So...
Make sure there is plenty of terrain on the board. Cityfights are good. Jungle fights are better. Use anything you can to arrange close range (12" or less) firefights where you have two or three squads-with flamers & heavy flamers- against one of theirs.
You have to control the tempo of the battle and the location/situation of the firefights. Perhaps some of the better Eldar players (those who actually know how to use Guardian Defender Squads) can suggest ways to do that.
