The heroes @FraVit93 mentioned will give you a solid team for the content of E&P. The special attacks of these heroes are the most important ones you want to have. (Also, the comments of other players are straight forward right!)
However one solid team will not excel in all aspects of the game.
For titan fights it is smart to leave out heroes with the weak color against the titan (same color as the titan; Wu Kong as exception) and use at least 1 more hero of the strong color.
Example Red Titan: Blue - Blue - Purple - Yellow - Red | Or a 3rd blue which you switch for purple or red. Yellow, Wu Kong, is a hero you will want to keep almost always in titan fights.
Necessary heroes for titan fights (upgrade these first if your primary focus is titan fights):
Gormek, Wu Kong, Kiril and Grimm
Other useful heroes for titan fights:
Rigard, Little John, Sonya, Scarlett, Sabina, Merlin, Caedmon & Melendor
This once again depends on the color of mobs/bosses and their special abilities. Threads on this forum have already discussed what heroes you ‘should’ use. Looking at your bench of heroes and their special attacks, I would suggest to certainly use a few of the following heroes for these events:
Gormek - defense debuffer and AOE hitter
Scarlett - attack debuffer
Rigard - healer + cures status ailments from your heroes
Sabina / Melendor - healer + removes buffs from enemies
Merlin - prevents bosses using their special attacks on you
Wu Kong - no explanation needed
Chao - I prefer Chao over Hu Tao and Li Xiu for attack teams, because his special deals more damage as a sniper. Mana reduction is useful for bosses
Sonya - single sniper and removes buffs from all enemies
Kiril - boost your defense and attack
Grimm - defense debuffer and AOE hitter (like Gormek)
Caedmon - single sniper and removes buffs from all enemies (like Sonya)
Little John - Mana reduction is useful for bosses (a bit like Chao)
It is important to use the right combination of heroes so that there is no overlap in special attacks.
Let’s use Guardians of Teltoc (reflect color yellow) as an example. I would stack double or triple on purple color heroes. I would use Merlin (mana control), Sabina (heal + buff removers and more tile damage compared to Rigard), Gormek (defense debuff + aoe hitter) for sure. You might want to add Kiril for the boosts. You will need a sniper. Caedmon will suit better since the event yields green mobs in the first 2 stages. Or you double on red to counter the green mobs and use Kelile as sniper.
Your team could be: Gormek, Sabina, Merlin + Kiril/Caedmon/Kelile.
But hey, you don’t have a hero who cures your status ailments now. So maybe you do want to switch Rigard for Sabina and use Caedmon to remove buffs from your opponents. As you can see, there is not a single approach to these events.
Let’s assume you’re looking for a rainbow defense team.
Kashrek is your number 1 tank for your defense team. I usually stack 3 red color heroes against him, but often he fires his special attack neverthless. Problem!
Wu Kong in your defense team isn’t such a great addition. I personally think Li Xiu (or Chao, but Li Xiu is better in defense) is more annoying to play against. Li Xiu could also serve well as a tank.
Grimm is a nice addition for your defense team if you place him next to your tank. That way his special attack has a higher chance of being used. If your tank is Kashrek, then Grimm will also absorb less damage from tiles if your opponents stacks red heroes and uses red tiles to attack your center. If Kiril his special goes off, then your opponent will need to remove your buffs or else it’s going to be a lot harder for them to beat you. I would also position him next to your tank, since he has average mana for his special attack. Sonya, just as Caedmon are nice snipers.
Gormek would currently be the best red for your defense team. A case can be made wether or not you should use both Gormek and Grimm in the same team.
From your healers I think Melendor is the best one for your defense team. Considering I favor using Merlin instead of Sabina or Rigard, Melendor would be my first choice. But maybe, when using Kashrek as tank, you don’t need another healer. It’s a personal matter.
I would always include, based on your current available heroes, Gormek, Merlin and a healer. The defense teams I would aim for and try out are:
Sonya, Gormek, Kashrek, Merlin, Li Xiu (Chao)
Sonya, Melendor, Gormek, Merlin, Li Xiu (Chao)
Caedmon, Gormek, Li Xiu, Merlin, Kiril
Considering you have some heroes leveled to 3/60 already, I would suggest you to work towards this defense team:
Sonya, Little John, Gormek, Rigard, Chao
Just as @King_Nothing said I would also replace Little John for your defense team. Caedmon or Kashrek will be awesome replacements. Since you will want to keep Wu Kong for titans/events, you might want to stick to Chao also for now instead of leveling a fresh Li Xiu. I do this myself. He’s not bad and useful for events as well.
Sonya, Caedmon (start leveling), Gormek, Rigard, Chao
Sonya, Gormek, Kashrek (start leveling), Rigard, Chao
I am someone who stacks colors against the enemy tank. I will always go into a fight with a setup, such as: 2-2-1 or 3-1-1. Taking this in mind I will write more now.
The heroes who will really rock, and which I would upgrade if you want to focus on raid attack, are:
Kiril, Grimm, Caedmon and Merlin. I would also upgrade Scarlett. Wu Kong is awesome, but his gambling stance is unreliable. I would favor Chao or Li Xiu, but you’ll want to upgrade Wu Kong for other aspects anyway.
This way you will have 2 reds (Gormek/Scarlett), 2 yellows (Chao and Wu Kong), 3 blues (Kiril, Grimm, Sonya), 2 purples (Merlin and Rigard) and 2 greens (Little John and Caedmon).
A rainbow attack team you can aim for could be:
Kiril, Gormek, Caedmon, Merlin and Chao
A rainbow attack team you can use more quickly could be:
Gormek, Sonya, Caedmon, Rigard and Chao
I repeat: “However one solid team will not excel in all aspects of the game.”
Wu kong - without doubt, start to upgrade him. I would leave Chao at 3/60 for now. Unless you have enough materials to ascend both, I would ascend Wu Kong first. If you have enough, you might want to ascend Chao and bring him somewhere to 4/30 - 4/50 before working on Wu Kong. That way you can have overall a better rainbow team for events and quests. It should not take more than a few days.
We all agreed that you should replace Little John with either Kashrek or Caedmon.
Caedmon - can be used for everything, so I would choose him.
I would continue to upgrade Gormek and Sonya, but you can also choose to upgrade Kiril instead of Sonya.
Same counts for Rigard vs Merlin. If you have enough materials, I would definitely ascend Rigard first. Just for a steady rainbow team first. Next in line will definitely be Merlin though.
This leaves you with the focus on:
Wu Kong (& Chao), Caedmon, Gormek, Sonya (& Kiril), Rigard (& Merlin)
Adjust to the color of the titan, but include Wu Kong / Gormek / Kiril when possible. Same basically counts for raid attack teams.
Sonya, Caedmon, Gormek, Rigard, Chao
Caedmon, Kiril, Gormek, Merlin, Chao
Rainbow attack teams for quests and events:
Same as defense teams, but you can replace Chao with Wu Kong
There are more ways to build up your team, but this is how I would approach it. Hope it gives you some more insights on top of those which have been given in this thread already!