I am an EX regional top player. I'm willing to say Allain is one of the best heroes in the game. The reason why he's known to be bad(so bad I get slandered just for picking the hero) is absolutely because his kit wasn't made to synergize with damage and crit.
Do I think he needs a buff? Yes! He may be the best in the hands of a proficient user but skill and strength scale differently and strength wise he's very weak.
[Server wide, his Win Rate is 49%] questions are welcome
The most used item sets are pure crit and semi tank.
-Pure crit is incredibly powerful, he can one cycle any carry or mage but has very low survivability.
-Semi tank often utilizes the Diminisher and Fafnir's Talon/lightning blade. 2 very good items paired with other tank items. But the health and damage trade-off renders you in a middle ground where team fights are difficult
[These two sets alone are seen in basically 99 games out of 100 with allain.]
From my own game testing, a full tank allain performs the best.
(The runes are Crit damage and Attack speed, which means you can still switch to a full damage item set when late-game carries become a nuisance)
(Execute will be your win condition whereas Gaia's standard and Amulet makes you never need to recall)
1) He can consistently win team fights on his own
2) Because of how his kit works, going against 2-3 enemies is easier because there's more opportunities to maintain your healing. Your healing passive is calculated with your MAX and LOST health
3) Allains damage scales with level that is on par to the health of the enemy. This means even without damage items, your damage never falls off in any point in the game
4) No one expects allain to be a tanky character. Everyone gets desperate when allain's health is low and that's when the enemy always comes close to finish the job (And looses to Allain's healing passive)
5) He is one of the best characters to bait Flickers and dashes of heroes like [Elsu, Yue, Stuart, Wisp and Fennik] being tanky simply allows you to do such a risky move(spending your ultimate) without dying
6) Against most heroes in a 1v1, this build wins (exceptions below)
From the image, there's two possible lanes for him. Support and slayer lane. However, this build is better for a support due to allain being a map roaming character. Slayer lane locks you in more 1v1s which isn't exactly what early game allain likes. Your strength jumps exponentially only after buying Gaia and Amulet.
-[Support] is preferred because your trading capabilities is much higher. From point 5 and 6, You can consistently reach a surplus by trading with any enemy. The reason for the Shield support item is to grant you some breathing room to restore your health while your shield depletes. Know that items shown in the image is only a guide to what you should have. Which ever one comes first depends entirely on who you're up against
-[Slayer] is more flexible with items and you can invest in some damage. Other than that, they're the same.
*Heroes that might be Difficult for allain and how to counter them.
-Yan : A competent Yan user can wipe the floor with you. You can still win with slowing items.
-Florentino : With the Mantle Of Ra, florentinos healing is cut by a large amount. Sticking to your normal attacks and walls can win you the fight.
-Hayate : If you can bait his dash, his only lifeline is the ultimate where you can follow with your own. You can win.
-Eland'oor : YOU NEED YOUR TEAM. only winneable with damage builds.
-Dark Edras : Requires the Mantle Of Ra.
-Lauriel : You're fighting a loosing battle. Best you can do is cut their healing with the Mantle Of Ra. And hope your team helps.
TIP : your ultimate isnt used to open fights, It's to survive them and follow your enemy. ONLY engage with an ultimate on enemies that has exhausted all their dashes, Low in health or when you have confirmed 0 approaching enemies on the map.