Retrodes: You can also snipe them from the corners of wall-less corridors. If you turn into a hallway perpendicular to an approaching Retrode, you can safely snipe them across the gap while their beam attacks can't reach you.

For Phantoms, I find it usually a -bad- idea to run away from them, especially if you intend on actually fighting in the Graveyard rather than just make a clean run through and if you're in a full party. While you're not just summoning more Phantoms to get on your trail, you're also summoning more zombies as you cover more ground that can easily block and overwhelm members that are lagging a bit behind, making them easy pickings for Phantoms. If you make a wrong turn and come to a dead-end, you have to go back, dealing with the Zombies AND Phantoms. I recommend dealing with them swiftly as they appear, the party focusing on one Phantom at a time to avoid being mobbed by the others. They have a distinct pattern of attack- a three-slash combo and a charge attack with pauses after each attack. Its best to wait out a combo before hacking at them using a sword (don't combo- shield and get out of the way of its next attack). If it starts charging an attack, simply run around until it releases it- the charge attack rarely hits as long as you're running away from it. Otherwise, you can snipe them easily with guns and bombs (freeze bombs work wonders) as they don't make too much effort to dodge. The Phantom doesn't take a lot of damage and can be easily dispatched with enough focus.

Attacking phantoms while they're charging, then shield bumping and running away, is quite a good strat. Make sure to dodge the flying swords if they have them.

Another tip, Trojans will use their charge attack when you're standing still. If you're fighting a Trojan by itself, you can just bait the charge, dodge when it comes for you, and then go around to their back and hit them as they swing and miss you completely. The whole attack is easy to dodge, since it's set on its path as soon as you see the warning spikes, and the Trojan will swing at where you were when it began the charge, so all you have to do is move to either side once you see the spikes.

If you're fighting a Trojan that has a few friends, you should keep moving, so a gun would work well here, possibly picking off the others, then using above strategy once you've got it alone.