Would that work? Would I be able to defeat Hell Baal by myself?

you will need a few curses to go along with your summons. amplify damage, decrepify and dim vision are the best necro curses.

After making a Summoner roughly 5 times, I preferred Life Tap because my minions almost never died. (some would die on occasion with those Lightning enchanted monsters)

Amplify Damage = Big radius. Benefits your Skeletons and Revives.
Life Tap = My minions rarely died, but slower kill rate. Better safe than sorry in my opinion.
Decrepify = Radius is too small and mana cost is a bit higher, though I may try it this time around.
Lower Resist = The only curse that is good for PvP. Cast Lower Resist and revive a bunch of Lost Souls. (those lightning ghosts)

Any other curse sounds useless. ;)

I do see some Summoners use Corpse Explosion, though it's not my style.

Good luck! :)

Decrepify and Amp Damage have a good possibility of removing Physical Immunity. Lower Resist also has a good possibility of removing Elemental Immunities. Dim Vision has its place in pacifying Lost Souls and other camping monster. They won't lob at what they can't see. I've found a huge difference using Decrep vs Amp Damage with Baal. Especially when you couple up a few cold mages and a clay golem. With a large swarm, his magical attacks happen a lot less often.

definitely. a summoner/curse necro can easily solo hell naked. I prefer all melee skels plus iron maden, the mages don't really do much.

All summons? No definitely not.

1 In all or most curses, just make sure you have life tap and decriptify.

Act 2 Offensive merc(Might Aura) and put the Concentration Polarm on him if you are rich, if not it is just as good without it. +1 Skills also help out the mercs might level I think, its been a while.

Life tap if your merc doesn't have any life steal or if he gets too low.

Decriptify on mini/bosses with a clay golem and at least a couple ice mages will slow them down by A LOT especially if the boss is heavy on the melee.

For normal enemies Amplify is ok, if there gets to be a lot , like say your skeletons are out numbered, I usually use Decriptify.

The common setup for a summoner is

20 Skele
20 Mastery
1 in all other summons
20 Corpse Explosion
1 In all or most curses
Rest into Bone armor Synergies

However personally I find it x10 as fun to not to use CE and go with 20 mages instead, although an army of like 25 mages is barley equal to a handful of skeletons, I still I find having them is more fun.