Does the target lock mean that melee will be limited to 1 on 1? If someone is locked on the player in front of them it would be easy to attack from behind.
If it is limited to 1v1 to avoid the tag team tactics it would work in the Eldars favour but the Orks may have to queue for a fight.

It shouldn't be 1v1, I can't see it working, plus you should need to rely on your squad. Its going to be hell for lone wolves though.

Edit: By 1v1 I mean a sort of "duel" state when locked on, where damage from players other than the one locked onto is at least partially mitigated.

Target Lock isn't a duel so there would be no damage mitigation at all. Target Lock doesn't change friendly fire either so melee still can't pile onto one enemy. Depending on the weapons involved could still probably surround the target. Other than that it would be unwise to gather around and wait to attack an enemy. Engage another target or leap frog attacks (hit and dodge away while another player continues the attack, repeat as needed).

Devs have only stated in a livestream that there may be a duel mechanic for challenging friendly players, they mentioned it being a designated spot such as an arena. I can see a duel mechanic applying to Hero classes mitigating damage from other sources but I doubt those would be a thing especially any damage mitigation while the Heroes duel.

Target lock provides benefits to fast moving characters too: easier to keep your attacks aimed at your enemy while simultaneously dodging around avoiding gunfire from outside forces. Enemies probably won't turn towards you while they're doing a melee strike too, so even in melee speed is still useful. They start a melee strike combo and poof! you're behind them stabbing their kidneys out. Which is, again, much easier when the lock-on turns you towards them and helps you roll around them rather than just towards/behind them.

Think Dark Souls. The lock-on there never devaluated high speed builds. Many people PvP in their bare chest to prevent armour slowing them down. Several of the top players, in fact.

Also, they can just give Eldar shorter animation times, too, or faster cancelation moves. Let's say a marine can't move for 0.5s after a melee attack, this could then be 0.3s for Eldar for instance, which you will definitely notice when going for quick strike->parry follow ups.

So many possibilities for implementing Eldar speed in a lock-on system, people. Don't freak out.

as i see it, it will be like dark souls where you can simply choose your target and thats it, you still have to reach your opponent to make your attacks hit, and know when to roll,block,parry etc. if they deliver the agility eldar are supposed to have i don't see any problem. having played space marine, i can tell you, having to turn manually was a pain in the ass because it felt like you didn't have control, besides, EC has blocking, parrying and dodging while space marine only had dodging for the tactical classes and the jet pack for the assault, that's why it makes more sense to me for EC to have it.

Thanks for a lot of good responses.

My main concern is Orcs and Mehrines being able to turn to face no matter what you do. If this can be mitigated without too much trouble, I won't be worried. What I also don't want to see is the Eldar being the ones that have to do all the compensating to make this happen (we do enough compensating for the Mon-keighs already ). The Orcs and Mehrines should have to work hard within melee to get a chance at attacking a fast moving Eldar, not vice versa.

I like the idea if it's directly between two heroes. The two of them go head to head with a damage mitigation attached, that's awesome and lets my Val'Gorbak beat the everloving shit out of an Autarch.

However, no way this should be between normal units. Tactical marines versus Chaos tac should never come down to a duel.