Well if you read my roles tutorial you'll know that Ice and Earth basically have the highest defense. So if you're going to tank, and you're not very geared, your best bet is to go the path of modding your gear with Dominance & Health mods. Now the bytes for this plan are solid blue, meaning they are fortified bytes. Depending on the item level of your gear your want to mod accordingly. So, by modding all of your blue sockets with these mods you get all of your socket affinity bonuses. Now for your yellow sockets you will want to either mod them with Dominance & Power mods, or Health & Power mods. These plans will involve you getting green bytes, called durable bytes. The red sockets will be similar, but you will be looking for Dominance & Precision mods, or Health and Precision mods to get your socket bonuses. The bytes are purple, or vengeful bytes, but based off of your power you could use Might instead of Precision mods. Fire, as well as Ice, use a lot of their moves to keep the aggro off the team, in turn helping to burn down the enemies faster helping your team out as well.
Once you get your gear high enough, most of your dominance will be coming off of your gear, but that doesn't mean you should let your gear do all the work. As you progress for the gear, you will earn more skill points allowing you to spec into innate skills giving more dominance, as well as health.
Being a tank means keeping all of the aggro off of your team, meaning you have to be up in the enemy's face at all times. You're going to want a melee weapon such as, Martial Arts, One-Handed, Dual Wield, Staff, Shield, or Two-Handed.
Healers typically just stay back along side with the controllers. The types of mods that healers use in this scenario should be as follows: Health & Restoration, Restoration, and Restoration & Precision. Restoration are solid yellow bytes, so mixing yellow bits with any other color will give you your durable and tenacious bytes. When you earn more skill points, you will want to spec into all of your extra restoration innate skills, as well as your critical healing magnitude, and critical healing chance innates.
Going back on what I said about healers staying back, you will want to get a long range weapon, or a weapon sufficient to where you will not take very much damage. (i.e: Bow, Dual Pistols, Hand Blasters, and Rifle.)
Like I mentioned before the controllers usually stay back with the healers that way the healers have a constant power supply. The mods that your controllers should be socketed with can somewhat be varied, but for the most part this is what they should be socketed with: Vitalization, Vitalization & Dominance/Health, and Vitalization & Precision/Might. Typically the weapon of choice recommended for controllers are the Dual Pistols, because they give you back power a lot faster as well as build your super charge up faster. The controller with the higher vitalization should be giving out Power Over Time (PoT), and debuffing. The other controller should be focused on spamming their instant power moves that gives back power to the three most fatigued group members. While you accumulate your skill points for your innates as a controller you are going to want to spec into all of the extra vitalization, and cunning innates.
As a controller, you will want to use around the same type of weapons as a healer. Like, I said , you're not inclined to abide by what I say by any means, however you can choose whatever you want to use.