Nothing is "least useful" Everything is equal. Its about the guns and players

All classes will be relevant, everyone said hunters were useless in Crota till they figured out you could use invisibility to effectively down Crota. Certain sub classes are more relevant than others, bladedancer, sun singer and defender are all better imo for raids than their counterparts.

I'm picturing 3 Titans, 2 with alpha luppi and 1 with helm Saint 14, it will be an endless bubble

We really can't say anything until gameplay of PoE is revealed. Right now every sub classes could be useful or not as useful.

All of the classes have strong defensive abilities. Hunters- When needed can go invisible with Blade dancer, activated with a Super, by crouching, or even meleeing enemies with Blink Strike. Don't touch me's provide the invisibility trait as well, combined with the Shadow Jack perk, and hunters can go invis for quite sometime, quite often. That has to be helpful. Warlocks- Fireborn in Radiance gives them an extra life. In addition, they get an additional shield with Scorch by meleeing enemies, keeping them extra protected, so they can keep up the dps onslaught. Titans- They have their Ward of Dawn bubbles, giving themselves and the group bonus dps damage with Weapons of Light, or bonus shields with Blessings. Not to mention, the bubbles are a great place to take cover. In addition, throw on a Saint 14 helm, and now their bubbles blind any enemies that enter it. Top it off, Titans can get an added shield in Barrier by meleeing enemies. All of these attributes should help fuel any team to victory. In my opinion, the best team is likely one consisting of one from each class. This is grating the unique benefits and qualities of all three to your efforts. Probably a formula to win.

Hunters can suck Deej nutz...

Considering we have no clue what to expect I'll wait to answer.

I only said hunter because their supers are more pvp based, while both warlock and titan have an extremely useful crowd control(foh and nova bomb can clear out groups easier than the hunter supers), and a good defensive measure(self revive or radiant skin for warlock sunsinger, bubble for defender titan). Golden gun can take out groups of low tier enemies and bladedancer is good for escaping, but the other supers are more pve based

Seems as if most people have the same sentiment as myself. Which is "NONE OF THE ABOVE"! Like people have said no "one class" is useless or least useful. All have strengths and weaknesses. Titan: close proximity attacks and defense. Both very helpful but both are used for something very near you. If you decide to fist of havoc something farther away without you team, you risk seperating yourself from your group. It's not always needed to attack something right next to you. Take Crotas end for example. Heavy armor. Good recovery. Terrible agility. Hunters: bladedancer can be useful but runs high risk/low reward for supers. It can be activated and extended to a longer range and still return to group, but is dangerous. Gunslingrrs get a lot of hate but honestly it's the longest range super attack there is. Yes maybe it's weak, but it can be very useful for long distance targets, especially with arachnid helm. Fast. Agile. But very prone to extremely slow recovery. Warlocks: both sunslingers and voidwalkers are useful, however, many sunslingers decide not to use the class perk to help teammates generate grenades swiftly when in close proximity. Self rez is good but should not be used as a crutch. Voidwalkers with obsidian mind can generate lots of orbs. Mid range supers to long range supers. Extremely helpful when used correctly. Which ist people don't. Recovery = perfect. Agility good. Not too much armour though. We see trends that signify that all have something to offer the other class in both class specs and in damage regarding supers. When meshed well with guardians who know what they are doing they equal something bigger than the addition of all the parts. Oh and last time I checked, we use guns 90% of the time NOT SUPERS. Since that's the case we are all mostly equal until the shit hits the fan. And when it does I hope to have a fire team of EACH CLASS. #knowledge

Don't know yet but i can't wait to try it with 3 Titans with Helm of Saint 14...Blessing of light, armor or light and weapons of light

Every single time. Every time I come across some poll saying, "Which class is the best?" or "Which class is the worst?" or something along those lines, Hunters always get the bad end. I don't understand why. Every class has its perks and drawbacks, how is Hunter any worse than a Titan or a Warlock, and vice versa? Personally, I just can't comprehend the oppression that Hunters get.

Probably hunter. Only because of the tankish nature of the other 2 classes. If it is horde mode than bubbles and self res are both pretty good skills to have