Anyways, I will try my best but the important elements for assassins is knowing the basics which are as simple as “stutter stepping” for auto attackers.
The harder parts are timing, it’s quite similar to tanks/healers timing their cooldowns correctly to be the most effective, but instead the assassin tries to follow up with burst or attacking that such target that was locked in place, those are simple but tend to be effective as assassins are the best at follow ups, if they of course follow up in the first place…
Being the priority of the DPS in the team you have to learn to keep some cooldowns on check, it really depends on what you are playing, e.g Raynor can use Q in both ways, to finish off the target or create a gap between you and them, Tracer not using Blinks or Recall poorly and instead abuse her ability position constantly, Valeera playing a game of patience, chaining her CC on a target or applying just legitimate pressure on someone, the list goes on. ← This also depends on what you are facing.
Raynor, is quite simple but also can be complex even though people call him braindead easy, it is true that he’s pretty simple but his ceiling is pretty medium to high levels.
I should just point out the most of things to use but for starters:
(I have no idea the names of the abilities so bare with me)
Q Ability
A straightforward knockback shot with damage on top of it, it actually goes both ways, on one side it is good for an extra layer of burst and procing talents like Ace in the Hole on the other hand it behaves as an anti dive response ability creating gap between you and a target, talents like “Paint them Red” makes this talent more effective in both roles mentioned here.
W Ability
This can be frequently spammed if anything, its pretty much his main damage increase when it comes to sustain, there’s barely much to speak of this, it basically increases your attack speed which also requires you to learn to stutter step (attack → move during the delay → attack again) to keep your position safe or keeping yourself in your target range.
E Ability
Healing, also straightforward but depends on when it is the right time to use it, for example meaninglessly using while healers around you and not being pressured (at the moment) would be meaningless to spend it, otherwise its good to counter anti burst especially with certain talents that makes it grant armor to counter inevitably death, talents like Fight or Flight makes this talent better against Burst damage with the armor layer on top while being on much lower cooldown.
Hyperion
A zoning and pushing power, I always go for this during objective pushes and try casting this to get more pushing power involved while still pushing the enemy away.
Raynor’s Raiders
A pet heroic allowing you to control a banshee on the battlefield, very good in checking bushes or adding an extra layer of damage, if you play rexxar you probably find this quite similar, just make sure you keep up with it and don’t let it die carelessly, that’s bad.
For more info over some the talents you can always give the ice veins guide a shot, which in a much broader detail over raynor and his talents, the list is also quite accurate with the current meta he is in: