Ok, so my maxed 5* greens are: Alby +18, LotL +18, Telly +18, Lianna, Kingston, Morgan le Fay, Gregorion & Tarlak. I’m at 9 tonicums, and enough blades and tomes. I have an absurd amount of choice for my next green 5*, and I can need some advice which to level next. The list is: Heimdall, Ratatoskr, Atomos, Margaret, the Hatter, 2nd Alby, 2nd Evelyn, 2nd Telly and 2nd Kingston. Also 3x Kadilen.
Yes I know ;-), but I still can’t decide…
So my reasoning is as follows: I have enough snipers and a good normal tank (Telly). My war tank is Lotl btw but may get the bench for Telly. Alby is in my normal defense team, so Hell +18 is tanking there. Alby also joins all my raids. For raid tournaments Lotl is great for rush attack, especially when red is left out. Tarlak is great for the titan (and is joined by Evelyn, Kingston, Gregorion and Buddy).
So Alby takes care of resurrect, don’t need a second one, and this kinds of leaves Heimdall on the bench. A lack of blue wartanks makes a second Evelyn not a great choice, enough snipers to not level a second Kingston. Hatter is fun but doesn’t feel like a strong choice. I’m leaning a bit towards Ratatoskr as pure green healer after LotL and can be fun against the Titan. Atomos would be the second AoE attacker after Telly, could also be interesting, but won’t take the tank position from her, and I read a post where people who tried him after his recent buff, and they were not that enthustiac. A second Telly could be the compromise between Atomos for damage and Ratatoskr for healing. Heimdall gets an A+, so that’s that, but maybe also have to look at his other skills and not focus on him as a lesser Alby (lower resurrect skill). And I had trouble raiding Heimdall tanks. But is he better than Telly +18, even when I start giving him paladin emblems?
Telly is no 1 tank.
Personally i’ve never had problem with heimdall
Maybe we should just declare that you are the winner!
Other than that…Hatter or squirrel. You have another utility heroes, go for something fun 
I’d go for Rattatosk for the average speed heal and the big titan damage. Otherwise I’d consider Atomos if you want to run a big Atlantis fam team, or Hatter for fun.
As you have enough depth in your green roster for raids, events and so on, i definitively would go with the squirrel. Its a bit niche, but it will further increase your titan scores. 
I won’t say the other suggestions are bad, they are certainly the most logical. The only dark horse I may consider is Kadilen. She is better than most think and if you get her maxed in advance and are lucky enough to score her costume you’re in business.
Good luck though, congrats on your glut of green success!
Thanks all for the great comments, the early return seems to suggest Ratatoskr, so I’ll look hard into that. Interesting suggestion to look again at Kadilen, will do!
And thanks for the first place @JonahTheBard much appreciated. I feel lucky with green from the start of the game, my first hero I pulled with a paid one was Alberich. Nearly fed him to Bane because I thought slow mana was bad…
I’d go Margaret. Her attack stats are amazing and you could prob replace buddy in your titan line up.
Kadilen would be be second choice… have her costume?
No costume sadly, just three copies. Interesting suggestion for Margaret. I have Buddy in my titan lineup only for defense down, the only green hero that does that I think. Tile damage of Margaret is insane -especially with sword path emblems- and dodge increases survivability, but her special damage is not great on the titan…mmmmm
Heimdall. His att boost is very powerful against titans and bosses. Simply double up the health of all and give your team 30% att up.
The squirrel is a cool green healer, but there often won’t be many boosted tiles on the board.
Alby and Heimdall together are a very nice rezzing tag team.
It depends upon what you want to do. But as someone with 8 different maxed greens and 4 other sitting at 3/70 I would go for the squirrel next, just more fun.
Mainly to just go nuts (pun intended) against titans and try to break 200k for a new record. Full mana pots, Scrolls of Alteration, Titan Banner and then see if Hurricane/Tornado or Time Freeze is best. Using 5 Scrolls of Alteration tends to shuffle the board quite a bit on their own. Probably Tornado though, Hurricane is too expensive.
Well, with the tonic from Shrikewood and one from the offer, I’m suddenly up to 11 again. I hope to get another one when I have upped Ratatoskr, then I can also start on Heimdall. 1st world problem solved Thanks for all the advice guys, definitely helped me to go squirrel this time…!
@mrslam23 can you post screenshot of your heroes.
Which ones would you like to see? All my green 5*?
All of your heroes please. I just want to see which of your greens are also good to be paired with other elemental heroes of yours. Thanks.
You could just go 2nd Evelyn
Thought about that, and although she is a staple in my green teams (Titan, War, Raid) because of elemental defense down, I’m second-guessing the worth of a 2nd one. I could use an extra one in the war, but we encounter seldom a blue tank. When Aegir came out, this was different, and maybe Raffaele will change it a bit, but I don’t think so. What’s your thinking to suggest a 2nd Evelyn? Thanks!
But since you are already adept of raiding with Alberich in it, wouldn’t it be beneficial for you to attack in war with another team with him in it?
Given that you have a pretty decent green roster (and decent is an understatement in this case.), I’d say Margaret is a solid choice. She’ll help her neighbour heroes survive - whichever team you put her in. (Similar comments for Kadilen costume - However, you don’t have it.) And her attack stat will help further boost your titan scores.
Why not Heimdall? Because that fat guy does his job just fine at 3/70. If you don’t have plans on using him as tank (which you shouldn’t have- you have a Telly+18! Your tank needs should be covered for the foreseeable future), then he should sit at 3/70 for the foreseeable future.
When I got him initially, I completed the third stage - the difficult one - in an emblem quest with Heimdall 1/1!! 
His overheal is that powerful! And it maxes out well before 3/70.
This should not be a big factor.
While forming a titan team, the focus should be on maximizing tile damage (special damages hardly tickle a titan). This is what conventional wisdom dictates, and I am yet to see an exception to this idea. 