in this discussion (i sound like a kixeye team worker, kinda wish i could help in other ways) im going to help you fully utilize your Standard Javelin tank to be the bane of all airborne and aircraft on the battlefield.
At its max lvl of 11 the Javelin gets a speed of 2.5, hp of 26,890, range of 625 (which gets a 20% boost against anything Air based), and a dmg of 5,575.
This may not seem like much to work with but i can Assure you (sadly i dont have them) Javelins are still a long way away from being replaced. First off the Javelin is the ONLY unit with a range farther than 550 (that is achieved by lvl 20 Commandos, BFGX with tightbore barrel, and lvl 20 Cyclones). The javelin fires a seeking rocket that CAN be shot down. however Javelins usually travel in packs of about 5 reducing the chance of their rockets being shot down.
The javelin can be customized with a variety of components including: Anti-Air flame tube which at max lvl replaces the "Seige" weapon with a fiery blast rocket that deals a giant fire effect and plus 5% dmg, the Anti-Air rifling grants a + 60% dmg against air when Defending a base which is useful for taking out pesky Hailstorms.
Javelin Missile: as stated the Jav missile can be targeted by anti-rocket defenses. in the Jav Missile comp you can add the Rapid Burst Ammo which at max lvl grants a minus 60% reload time good for quick assaults.
Ryu-Kai Treads: the Alloyed Treads allow the Javelin, Scorcher and Guardian a 30% movement speed increase and a minus 60% Effect and Duration against the Cryo Status Effect.
And finally the Ryu-Kai Armor: Beveled Armor grants minus 30% dmg from aircraft at max lvl making your Javelin a lot better at taking air that get too close. Aegis Of Goro grants minus 12% dmg taken from all which is good for the all around dmg reducer to ALL dmg types. Finally the Ryu-Kai Plating grants minus 30% dmg from turrets (like Microwave with range of 700) and an astonishing minus 2% taken from all for EACH RYU-KAI WITH SAME TECH IN PLATOON. this is by FAR the best armor to equip granting if you use the Scorcher, Javelin and Guardian together you can get a HUGE dmg resistance making your Wardens Seemingly invincinble. 
Now the Tactics: the main tactic of the Javelin is to sit back and watch as your missiles take out enemies from far off. however since they cant target ground its best to put a scorcher or a guardian with them to protect against units that try to ruin the fun. Javelins working alone are advised to always be on the move. Hit-and-Run or "Guerilla Warfare" tactics may seem wimpy but they can change the tide of a battle. with the range and dmg of a Javelin you can take down the mighty ESS before she has a chance to destroy you and floaters (nearly everybody has them along with floating heavies) you can destroy them and watch your opponents defense fall to the might of your Arsenal.
I hope this helps any and all who use the Javelin to make it your best anti-air tank in the field. Good luck out there!