Soul Reaper's main role is as a tank carry with a strong finisher. He has in the past been quite strong in the lane with his hp reduction aura and AoE damage and heal.
In the current competitive game, his slow and steady approach in the lane, limited ganking potential and low survivability means that he is unable to compete.
Why slow - very slow base movement speed of 290 which makes chasing, ganking and surviving extremely difficult.
Why limited ganking potential - his only ganking ability is his assistance is a low damage and low heal spell with a very high mana cost and in a gank you won't be able to last hit neutrals to recoup the mana cost with Inhuman Nature, coupled with a high mana cost ultimate that has a stun duration shorter than most lvl 3 disables/stuns.
Again slow movement speed makes it hard to keep up with a moving fight.
Why low survivability - No evasive or damage absorption abilities. Instead you have a low heal ability that is mana intensive. Again slow movement speed.
What to balance?
To make Soul Reaper viable, I propose to focus on his survivability, hp suppression, mana recoup and the role of his ultimate.
Survivability - provides Soul Reaper with a mechanism of surviving/avoiding a gank. Currently, players will pick up items to increase his survivability but in the early game, he needs something.
HP suppression - this allows Soul Reaper to establish his presence in a lane in a unique way by slowing and steadily reducing the hp of surrounding enemies. It is strongly themed, unique and synergises with all of his other abilities.
Mana recoupment - his mana recoupment off creeps is a strong feature of Soul Reaper and there is no better feeling than working down the hitpoints on a group of creeps, doing a 5 kill Judgement and getting all that mana back with Inhuman Nature. It really encourages skill based play.
However, there is no worse feeling than dumping all your mana in a team fight with no creeps around, finish off a hero and then stand there with 0 mana as all your skills are mana intensive and there is no recoupment for killing a hero.
Ultimate - his ultimate is a strong finisher. However, the superior magic 1.5 second stun is also a very strong stun in a team fight. I, and I am sure many have others, used it for its 1.5 second stun rather than the damage to secure a kill. I think the stun component should be improved to encourage the team aspects of the ability.
How to balance?
This will be the main source of discussion in this thread. Here are my proposals on how to balance. I will try to keep this conceptual with intentional vagueness in numbers to prevent it from become a suggestion/numbers fight but more of a conceptual debate.
Survivability - My preference would not be to improve his movement speed or add a damage suppression etc but to balance his other skills that still plays on his theme to increase his survivability.
HP suppression - the suppression as it currently stands is not sufficient to allow Soul Reaper to have a real presence in the lane. To establish such a presence I list a few balances:
Alternative 1: I would like to see a healing and regeneration suppression component to make this more effective in competitive play. A healing and regeneration suppression component firstly establishes great lane control through positioning and allows Soul Reaper greater control in the lane to combat aggressive harassment.
Alternative 2: To play on the Judgment theme, have judgement apply a debuff that reduces healing/regeneration much like Salforis but as a % rather than as a prevention. This will also synergise with his ultimate to prevent heals/regen during the stun leading up to the application of the damage. The debuff would be added via Withering Presence to encourage people to pick Withering Presence.
Alternative 3: Set his aura back to a flat range and increase the % hp removed per level.
Mana recoupment - Allow mana recoupment for killing an enemy hero and also from enemy heroes killed under the effect of Demonic Execution, either by adding a much higher static number for enemy heroes or make it % based like Blood Hunter. It allows you to remain useful in a team fight early game when you are still focusing on survivability items. Further, you can take advantage of the short cooldown of Judgement to hopefully heal yourself back into safety.
Further, it has been suggested that Soul Reaper gets a further effect from the damage dealt by Judgement like further enhancing his mana recoupment or adding a damage absorption shield like Nome's.
Ultimate - Two things need to happen to the ultimate to make it more effective 1 v 1 and also in a team situation.
1) Increase the duration of the stun or make it inversely proportional to the amount of hp left (e.g. less % hp left [e.g. 90% left] the longer the stun [e.g. 3.5 secs] but higher % hp left [e.g. 60%] the shorter the stun [e.g. 1 second].
2) Deal the damage at the end of the stun and the damage is calculated at the end of the stun.
This encourages the use of the ultimate as an initiator and definitely much earlier than usual. The damage is calculated at the end of the stun duration to take into account damage dealt during the length of the stun. With regards to displacement effects like Stormspirit, the ultimate will trigger at the end of the displacement effect.
I hope this thread has positively contributed to how we should approach a balance of Soul Reaper. I would appreciate people to point out any issues and I will edit this OP as required. Especially with any feedback they have from observing or being part of competitive play. I appreciate that two of the balance suggestions above are from the Dota 2 version of Soul Reaper and I acknowledge that here. I also acknowledge the different meta games and therefore have hopefully outlined why they are beneficial and also why the other balances are required.