Unlike Charge, Intervene additionally works to free the warrior of any roots and snares.
Tips and tactics
Be careful when using this ability if you're fighting ranged-weapon-using mobs, since you could end up intercepting a ranged attack towards a party member which is actually far from all mobs, and doing so you'll not only end up far from them as well, but also pull the melee ones near him.
On some bosses as offtank, when your job has ended you can help with the survival of the main tank by using intervene when he has very low health. You take one boss melee swing yourself, giving healers a bit more time to heal the main tank up. Be careful when using this though, because Intervene also reduces the threat of the target you use it on, so don't try it on threat sensitive fights.
Also, similar to the above, you can use Intervene's threat reduction specifically for that. Intervene a DPS close to the MT in threat for a small reduction in hate, allowing them to continue DPSing.
DPS warriors can use Intervene with a little stance-dancing. This can be handy when Charge is on cooldown, or simply to supplement this ability.
This ability can be useful simply in order to break out of roots and snares. Warriors can quickly Intervene to an ally or [War Banner], then Charge back to their target if necessary.