DS does not affect skills so the flames that WL shoots on his proc will not be made more powerful by DS, they will only cause damage based on his base attack. This is why War God is a good talent, it raises base attack so his procs are stronger. When I say revite is good on WL, I'm only really talking about revite 5/5. WL is an 'auto-proc' hero so his proc will go off without him needing to attack anything. This is great because he will give some of your heroes a shield at the start of the battle so if an enemy stuns or silences them, it won't affect those heroes. By contrast, if your revite 5 Atlanticore runs into a revite 5 Aries, it will lose all of its energy as it has to hit something in order to proc (Aries is ranged so will hit first and proc).

Cupid needs revite. Revite 5 is very powerful on him but even a 2 or 3 will help. He has a cooldown and in general, you don't really want zerk on heroes that have cooldown (there are some exceptions but Cupid isn't one). Aries is also really dependent on revite. Your 1st revite 5 should go on him and you'll be amazed at his power. By the way, you need to place crests that are different from your primary talent as only the higher level one will be active.

Orks is OK early game and you will probably find him useful for a bit but because he's a bit of a jack of all trades while not outstanding at anything, he'll become obsolete as you get more of the top heroes. DK is a better hero and has his uses even at end game. His proc does a lot of damage and similar to WL, protects your heroes (plus in-built revive 5 is very useful for a tank). SZ is similar to Orks in that he's an OK all round hero but becomes obsolete quite quickly, I wouldn't use any resources on him in your position.

Revive crests are good and yes LD2 is good for DK. I would probably get WL and DK evolved, then Druid and TG as they're cheap and then save fame.

For your reference, I'll list good talents for you to aim at for your top heroes: WL - WG/revite. Put any WG 3+ on him Druid - fine with what he has but replace with a zerk 4+ (unless you get PD in which case, 1st zerk 5 goes on PD) DK - LD/BW/revite Orks - fine with SS but don't spend fame to upgrade Aries - revite (really needs a 5/5 to unleash his full potential but 3+ is fine) Vlad - BW/WG TG - WG/zerk AC - revite 5 is his best talent so don't ever change, just should go to others 1st Cupid - revite 3+ (revite 5 is really powerful, big jump from 4 to 5)