Personally I think people are just too lazy to provide good info.
Anyway.
C3 legion would be the way to go. Something like this will handle all Anoms Solo. It does not really tank enough to tank a Outpost with the towers up so you have to kill a couple at least.
[Legion, C3 - Standard]
Corelum C-Type Medium Armor Repairer
Corelum C-Type Medium Armor Repairer
True Sansha Energized Adaptive Nano Membrane
True Sansha Energized Adaptive Nano Membrane
Heat Sink II
Heat Sink II
Heat Sink II
10MN Afterburner II
Republic Fleet Large Cap Battery
Caldari Navy Stasis Webifier
Heavy Pulse Laser II, Conflagration M
Heavy Pulse Laser II, Conflagration M
Heavy Pulse Laser II, Conflagration M
Heavy Pulse Laser II, Conflagration M
Heavy Pulse Laser II, Conflagration M
Heavy Pulse Laser II, Conflagration M
Core Probe Launcher II
Medium Capacitor Control Circuit I
Medium Auxiliary Nano Pump II
Medium Auxiliary Nano Pump II
Legion Core - Augmented Antimatter Reactor
Legion Defensive - Nanobot Injector
Legion Offensive - Liquid Crystal Magnifiers
Legion Propulsion - Intercalated Nanofibers
As for C4, unless you have nothing better to do they are not really worth it. I can almost guaranty (retardedness on the Legions side precluded) that 1 Legion in a C3 would just about beat 2 Geddons in a C4 from an income perspective.
The issue is that in C4s, everything is soooo far away. The Geddon just does not have the range or DPS to break reps.
if you really want to do it maybe something like this, I would test it on the test server first though as some waves technically break its tank and it is not going to be DPS tanking much of anything. (Mids are up for debate)
[Armageddon, C4]
Damage Control II
Energized Adaptive Nano Membrane II
Energized Adaptive Nano Membrane II
Reactive Armor Hardener
Drone Damage Amplifier II
Drone Damage Amplifier II
Drone Damage Amplifier II
Sensor Booster II
Omnidirectional Tracking Link II, Optimal Range Script
Large Cap Battery II
Cap Recharger II
Large Remote Armor Repairer II
Large Remote Armor Repairer II
Large Remote Armor Repairer II
Large Remote Armor Repairer II
Large Remote Capacitor Transmitter II
Large Remote Capacitor Transmitter II
Drone Link Augmentor II
Large Remote Repair Augmentor I
Large Remote Repair Augmentor I
Large Remote Repair Augmentor I
Curator II x5
Otherwise a Pally is king.
This fit is tried and test, and it will happily do sub 14 min Barracks (as low as 11min with 4% implants and some luck) if you know what you are doing (I pop an DC2 on the sanctums and and extra recharger for integrates).
[Paladin, WH]
True Sansha Energized Adaptive Nano Membrane
True Sansha Energized Adaptive Nano Membrane
True Sansha Large Armor Repairer
Corpus X-Type Large Armor Repairer
True Sansha Heat Sink
True Sansha Heat Sink
True Sansha Heat Sink
Large Micro Jump Drive
Tracking Computer II, Tracking Speed Script
Tracking Computer II, Tracking Speed Script
Cap Recharger II
Mega Pulse Laser II, Scorch L
Mega Pulse Laser II, Scorch L
Mega Pulse Laser II, Scorch L
Mega Pulse Laser II, Scorch L
Bastion Module I
Imperial Navy Large EMP Smartbomb
Imperial Navy Large EMP Smartbomb
[Empty High slot]
Large Capacitor Control Circuit II
Large Capacitor Control Circuit II
Hobgoblin II x5