You say, the ONLY thing Titans have is a bubble to distract boomers on Crota. (Which is actually an awesome way of completing it hard, it's so easy).
And weapons of light for Atheon (which again is awesome because you beat him so fast, granted you can beat him fast without it, but it makes it go smoother if you have someone lacking some firepower).
They can dominate pvp with their bubble set up (and recently infinite supers).
I'm not a titan fan myself, I prefer warlock pve and hunter pvp. But I am actually having fun levelling a titan, because they are so useful.
Fist of havoc is pretty fun to use too, especially jumping puzzle vog.
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I already stated that they are awesome for PvP, but PvE, they just make things a little easier, but it's still easy to survive without them, whereas, a Hunter is almost essential to be a Bladedancer for Hard Mode. (Getting that one extra hit is the difference between getting a wipe from Enrage and killing him just a second before).
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Titan is the only class that can support making them best for raids.