Barrow Blades is an enabler for talents requiring the enemy be burning. And possibility that it might do more damage than other skeletons (no way to confirm). Their summoning also ignites enemies.
Dread Seneschals is good for tanking aggro and CC.
So…what is the reason to choose Army of the Dead? At the very most it might be better for a spell spamming build maybe as there’s 6 sacrificial skeletons you can sacrifice maybe…but that’s not remotely worth the level 30 talent when you can already sacifice barrow blades and seneschals. Army of the Dead needs to make that EXTREMELY SHORT LIVED extra skeleton mean something…but they don’t because 1) specials ignore them and 2) monsters ignore them, which leaves them mostly useful for temporarily tabking a few more elite and chaffs.
On top of its current effect…
Suggestion 1: Skeletons all do slight bonus damage for each Skeletons attacking the same target. Making Army of the Dead slightly more effective at damaging sponges. Extra skeletons lasts way longer.
Suggestion 2: Army of the Dead skeletons also taunts specials and monsters to attack them. Extra skeletons lasts way longer.
Suggestion 3: Killing ignited enemies have chance to summon a skeleton. Extra skeletons lasts way longer.