We all know the game has some areas where balance is not perfect and some people have offered to make changes to balances things up in the past.
Here is a way I would look at it:
The real thing to keep in mind when looking at this issue is that most of us do play the game mostly out of nostalgia.
So if changes are to be made they have to be so minor that they wont change the way we play the game and the way the game feels/behaves overall we do not want to play another game we want to play warcraft 2 with all its mechanics and logic.
Ideally any change made would only make the game feel a bit better and make it more interesting to play without changing anything to its core mechanics and the way we play it.
In such a way that players coming back to the game wont really be noticing them too much, we are basically talking small tweaks in numbers nothing more.
Here are changes I would suggest if we were to make any update to the game's balance:
Lust has to be powerful it has to allow players to tare appart builings and all that jazz the only problem I see with lust is that it is so cheap players do not have to think about when to use it.
Players can afford always re-lusting everything without thinking twice.
I would thus propose to change the cost of lust from 50 to something around 100 mana making it a little more strategical to think about when to use the spell without reducing its effectiveness when it is.
Heal costs 6 mana per hit points healed a paladin has 90 hit points it means a full mana paladin cannot heal another paladin up as it will only heal 40 hp (edited).
the cost makes it not worth it to even use the heal in combat or even else.
I would reduce it making it twice as cheap like 2 or even 1 so that it will most of the time heal up the unit you are using the spell on.
Berzerker troll regeneration:
the thing is so slow the troll will die of old age before it get healed 9 hp. Archers on the other hand get a nice flat +3 damage I would up trolls regen a bit like twice what it is.
Coil is amazing firebolt not so much I would maybe lower its cost a bunch to make it more interesting to use it to for example taking down towers and other small objectives quickly without spending a full blizzard.
Or we could increase its damage by a lot so make sure that if you hit your target it was worth it.
They suck and they are expenssive I would lower their cost a bunch and make them use upgrades or make them a bit tougher but they still have to loose to a grunt 1v1 they are the units you want to make when resources are about to be mia on the map
A very powerfull spell to make dk bombs and other fancy moves but it is very expensive overall still and could be a bit cheaper from 200 to something around 150 100.
A fun spell when used wisely I would however lower the cost of flames shield from 80 to something around 50 to make it more possible/worth doing invisibility/flameshield combos.
Also it has a short range making it castable at a less close distance could help making it usable.
Also making it last longer or enable casting it on air units could help making it more useful.
A very powerful spell against other casters but it does cost a lot I would lower it from 200 to around 100.
These are suggestions that I feel would not change the game's logic and the way people play it but will encourage more interesting plays and thinking behind player actions.
Feel free to add your own thoughts on this and suggestions.
Tweaking numbers there and there as long as they do not de-nature the game is I guess acceptable in my opinion what do you feel about this matter?
Disclaimer: I am overall happy with the current state of the game and I am not saying we need to change anything. I am just saying that before changing anything we better make sure we have proper discussions about all of it so that we know what people are cool with and what not
Also it is a fun exercise to think of what small tweaks can change in the way the game is played even if it is to do nothing in the end.