SDGO MANIAC: Mission 03

Main TIPS

At least one tanker as difficulty rises
Only Beam SP on boss unit Apsalus II. Ranged and Melee SP do not inflict sufficient damage to units in missions but Beam SP help to hold enemy units on one spot for focus-firing (with exception of some boss units in several quests)
No melee-type unit
For quests that have conditions to destroy units other than Apsalus II such as Rising Gundam and Acguy, I recommend team players to bring Cyclops for faster clear (It really helps for finishing quests)

VERY EASY

Literally very easy. Any unit can be used but be careful with using SP since they only waste clear time and may cause glitches.

EASY

Minions like Doms and GINN are still not big issue to deal with. However, I tend to not recommend C-rank units from this difficulty since they are fragile against boss units and take longer time to clear the mission.
For quests involving destroying final stage units like Rising Gundam, you should either use Cyclops or use pretty strong range-type A or S-rank units. Melee-type units aren't favourable because Rising and Amatsu have melee-counter skill to cancel your attack and knock you down with their attacks.
For fast clear, all players just need to focus on attacking Apsalus II while ignoring others.

NORMAL

Now all enemy units feel tougher than the previous difficulty. I do not recommend units that are B-rank or lower for Normal difficulty.
Cyclops item is really needed for quests from this point on unless everyone uses strong S-ranks.

HARD, EXPERT

Everyone should use either S-rank or certain A-rank. Units should be range-type with decent power, ammo, and reload speed.
Generally recommended units to ensure finishing the mission are

Psycho Gundam - you can really feel how tanky it is in this mission
Apsalus II - attack from safe distance (at the exit of the narrow canyon path) with infinite Weapon 2 ammo and support your team with Defense Commander when your HP is low.
Big Zam - alternative to Psycho Gundam
Wing Gundam Zero - decent firepower with machine guns and twin buster rifle. Especially strong when Zero System is active.

Safest team composition - at least 2 or 3 Psycho Gundam with others as Heavyarms or other strong S-ranks.
Walkthrough

Everyone rush to the first net and destroy it as quick as possible. It will either be destroyed a little before or after first minion wave appears. Even when they appear. Focus on destroying the net first and then clear the first wave.

Not all players have to stay to destroy minions. One or more player can just rush to the second net while others fight Doms and GINNs to save time.

Do the same for the second net
All the above should take until about 3:00 which is when Apsalus II appears.
Before Apsalus II appears, a tanker (usually Psycho with the most health) rush to the end of the map (the farthest canyon wall) where Apsalus II appears. When the boss appears, it will turn around to you and only attack you until you are destroyed. While Apsalus is fixated on the tanker, everyone else must attack Apsalus II from either two tall rocks or use Cyclops on Amatsu, Rising and Acguy if you are doing quests.

If a tanker is destroyed, Apsalus II will change its target. If there's is a second target, take the first's spot or wait until the tanker respawns and Apsalus II starts attacking it again.
There may be some chances that Apsalus II does not attack the tanker first. This is either a glitch or another unit was nearer to the boss than the tanker.

I hope these help you finish your quests. :)

SDGO MANIAC