Hello, i will start with a short recap of your wall of text :>
-Fire Blade
--fixed basedamage increase (you suggest 20)
--basedamage increase by kills done (0,4/kill and decays after 3 seconds without a kill)
--Rarity blue/yellow (possible to stack them)
-Think about the item impact, and the differences (High Basedamage tower, like Balu or possibly Blofield Laser and in comparism, effect towers like Shadow or Scarface). The lwoer the base damage of the tower, the stronger the item gets (since they normally hit faster and have abilitys that multiply the effect). Go for some damage calculations, what would happen if you have 4 of them on a Scarface or Shadow and what happens if you go with that items on a Balu?
-About the set (fiery Shield or whatever ^^)
--Will give your Wizard a "Shield" which absorbs incoming damage. Instead of losing life you lose points of your shield first (thats the way i understood it ^^ i think there was another tower somewhere in the abyss of card suggestions with a property like that xD)
--Shields gains +1 Life / 5 creep kills (Maybe the shield decays too after, lets say 5 seconds?)
-Well the i think you should search the other hero (I'm too lazy right now ^^) and read about the "shield" there. IT is basically the same mechanic ^^
-God of Fire
--Probably a new Legendary Tower
--Which Race?
--Same basedamage Gain mechanic as your sword.
Hard to say much to the tower. In the end its a question abouit balancing..
General Note:
The big Problem with Cards (Items) is the huge problems while balancing them.
As an example i gonna take the Blood Demons Blade. it can yield (200 life +198 from the potion and weddign ring combo, [398 life, one life will be left]) a basedamage bonus of 397 Damage. Which essentially DOUBLES the damage on Scarface or Shadow, while on other towers its Bullshit [Balu, Dark Forge, Blofield....].
You have to keep in mind, that adjustments like this, MIGHT break the game. You have to put a lot of thougts into such mechanics. A Question you should ask yourself is: If they have yellow rarity, how good is the item compared to other Cards of that rarity. There are items like, Viking Helmet, which are weaker then Seven League Boots or that Yellow Steak thingy, but on the right tower [Shadow, Holgar etc...] the luck bonus makes it FAR superior. Every Card right now, adds somethin to different kind of towers and is balanced like that. What kind of towers should your item be used on and what impact does it have?
Ontrose addressed the balance concern pretty concisely. As for the computer question, Andy has taken it down. It was too much work to maintain three different versions of the game, and with the computer edition being so easily modified people were easily cheating up to ridiculous times and screwing the ladder.
Okay i got it , no computer version :P , as for the cards , i told you i'm quite new and this is one of my 2 card recommendations so... that's also new for me, i don't really know what to pay attention to , and i haven't gotten every single tower in the game , so its normal for me not to know some of the cards , but yeah , i put this as an idea if it is good or not , i am not the one to decide , i just thought it would be nice , and that's why you came after all , to correct me ^^
It's not about correction at all.
I'm pretty active on the forums the last months and always respond to possible new cards, since i would love to get more content in time, and like i said, andy does keep a tap on such things ;) even though not always responding.
But since i was a mapmaker in good old warcraft 3, i got some experience about balancing and such things ;) so i jsut give a some tips what to think about. I did not say that this idea is bullshit or anything, just gave you a few topics to think about and improve your idea, keeping a bit of the balancing work from andys shoulders ;)
I mean just one point is the fixed value of 20 damage to base damage ;) and the impact on different towers. Easiest way to fix it would be to go for 10% or 20% bonus damage. But in the end it wouldnt fix anything, since you wouldnt use it on the shadow, since there are way more potent stuff already out (Blood Demon Blade, which adds about 100% base damage... give or take a bit). On the other hand the Dark Forge and alike can benefit from it.
The way you described it, it would be too strong for early/mid game and utterly useless for lategame ^^
This is a chance to improve your idea ;) nothing more or less :>