There are two methods your group can choose between that are both equally successful at winning this fight. When one of the bosses is killed, the other will resurrect them as an untargetable, undamageable ghost that carries out its previous attacks, but appears to have no aggro table. For this reason, many groups choose to kill these bosses in unison by buring one to 10 or 20%, then the other, and then bringing them down together. The advantage to this method is that you never have to deal with the ghost mob. The disadvantage is that for the full length of the fight the party is taking damage from both bosses.
The second method for dealing with these two is to burn down Dalronn first. Yes, this does in fact mean that he will come back as a ghost and start throwing random Shadow Bolts at players. But, that is exactly what he did when he was alive. Doing it this way means that DPS can focus on one boss at a time and not worry about how synchronized their deaths are.
No matter what, do not burn down Skarvald first. This will almost always result in a wipe.
Because of Skarvald's random charge on normal mode it is advisable to keep the group all stacked on top of eachother. This prevents him from performing his Charge ability because it has a 5 yard minimum range. Skarvald does not do a Cleave, so there is no disadvantage to this positioning.
On Heroic Mode, however, the Charge has no minimum range and can hit anybody, even if they're standing right on top of him. In this case, it is better to keep ranged DPS and the healer at maximum range to increase the time that the Charge takes. After charging, Skarvald will return to the tank. The only time you would stack the Healer on the tank on Heroic mode is if the entire group but the healer is melee. If there is one player standing at range Skarvald will almost always Charge them, so if the healer is the only person with range then chances are that they are going to die.
The summoned Skeletons are vulnerable to all undead crowd control, like Turn Evil, Shackle Undead, and Traps. It is recommended that DPS focus on burning down skeletons as fast as possible, and then returning to DPS the bosses. The tank can pick up the skeletons, but doesn't need to. DPS should ensure that there is not a skeleton beating on the healer.