I thought i'd share my experience with forming what i think is the best party of monsters in FFXIII-2, ok heres the list and where to find them:
Chichu: Found in Archylite Steppe XXXAF throw mog into the patch of red flowers near the red cactuar statue that are just infront of the rock if you are facing north on the map, you will need advanced moogle throw to get it. Chichu is probably the best COM in the game because of its high attack and super fast strikes. when leveling up Chicu i suggest you use only the materials that upgrade STRENGTH only so all of the power droplets etc etc. this will mean fully maxed chichu has over 1200STR you may also want to learn him HP+25%/30% and resist magic/physical (from chocobo's or other monsters that have it).
Green Chocobo: Found in Yasas Massif 110AF/100AF. My favourite medic because it has one of the highest magics of the medic class and can also cause some physical damage with its feral link. Make sure you learn it Esunda and Curasa/curaja from a flaninator and it will be an awesome allie as it learns resist magic and physical and also fog (resist anti-magic spells from SAB class monsters). use all the mana materials you can when leveling it as it ends up with a good chunk of HP. if you are struggling to catch a green chocobo then a flaninator is a good second choice as its quick feral link Hyper Rescue is VERY useful for quick bursts of HP.
Silver Chocobo: Found by throwing mog into the giant green ball in Acedemia 4XXAF's academy centre (its where you meet up with hope and alyssa and platforms float around it with people on them, it looks like a digital sphrere. throw mog into it and you should get the silver chocobo (you'll need advance moogle throw for it to work). This beast is probably the best sentinal in the game, if you pump it with either all vitality or a mix of vitality and power materials it'll prove very useful in tough fights, Having a sentinal reduces damage to your entire party and this chocobo has a minimum of 7k HP when maxed and can go over 12k HP if you put the right stuff on it. It also has mediguard so you never really need to heal it, and its Feral link is the same as the other Choco's but its slightly more powerful. Also if you give it the correct abilities its the best chocobo for winning chocobo races (i'll try post a different guide up about that later).
What classes and monsters do you guys use and what style of combat do you prefer?
I used CloudBurst as my RAV alongside Narishima (big albino type behemoth) and a purple chocobo as my Synagist, i love the behemoth as it has really nice HP and has just over 1000STR and thats without fully using all power stuff, its a bit slow but its feral link is very good at damaging stuff. Cloudburst is an amazing Ravager as it can learn all the -aga spells off the bat and boasts some high Magic, also has a pretty damn nice feral link for uber damage. Purple chocobo i use because i prefer using my other characters as healers and attackers rather than buffers so my choco buffs me when i need a boost.
Cloudburst and Debris are very hard to catch and encounter, they are both very good Ravs but the blue chocobo is a good substitute. Narashima is another excellent COM and pretty rare, but i think Proto Behemoth is slightly more powerful but has less HP so either are a good choice.
I use the same set up as Mr Polish however before i found chichu i did use Narsharima a lot too as he was amazing, loved his high HP. Another good few to go for are Pulsework Gladiator (as a second option to Silver Choco) and Blue Choco (Rav instead of cloudburst/Debris) i also found Necrosis as a very good SAB role.