No I'm afraid those examples make Dan Angry, Dan Smash! (for the record I haven't seen any of the hulk movies but I couldn't resist the reference)
An example that I would like would be:
Card A = generically good but not great in any deck OR great in a specific theme but not so great else where - common
Card B = See A - rare
Card C = Potentially great effect but at heavy costs in any deck, or potentially AWESOME effect but at heavy cost and only actually AWESOME in a specific theme - extra rare
In my ideal balance system the above can be said for the card when used as either a soul card or a unit card, HOWEVER I can live with things and still be happy (just not AS happy) if the above is true for atleast 1 side of the card and the other side is weaker.
Now of course this also only holds true if we assume that every theme has a weakness, that is the trade off for themed cards being stronger, that because your limiting yourself to that theme your also gaining the weaknesses of that theme.
For example lets make up a theme, angels. In this themed deck all the angels recover HP whenever another angel attacks. This is a powerful trait of angels that might make them appear stronger then the average unit because other then that trait most angels are comparable to the average themeless unit in every way. HOWEVER when looking further you notice that Angel's ranged unit are actually quite a bit weaker then the average Refess ranged unit. Sure you can substitute in generic refess ranged units but then your close range units don't benifit from their angel trait as much. You can just stick with pure angels but then your going to have to build your deck to compensate for your weak ranged abilities.
This is an example where every card was useful but every card still had weaknesses. The generic ranged units didn't have the angel trait but they could still be useful because of their superior stats. The front line angel units APPEAR to be overly strong, but they are in fact balanced out by the fact that in order to take advantage of their trait and really make them strong your going to have to use weaker ranged units.
In my ideal balance we could look at all these cards and find similar situations if they're played as soul cards. Maybe they have effects that do cool things that are better then generic soul cards if you have alot of angels on your field, but in order to have alot of angels on your field you're leaving yourself with weak range so again the seemingly powerful effect has been indirectly balanced and while it will still be useful in pure angel decks, it won't show up in every deck. You might also have effects that aren't quite as powerful for the average deck, but are specially useful to a deck with poor ranged units. In this case what normally would be a weak soul card has been made a useful one due to there being a theme that can really make use of it.
And about the rarity issue, again the thing about high rarity is they need to be cool enough effects to be desirable, but still have enough weaknesses going against them that there not auto includes in every deck. Often you've got to build your deck around them to really get the most out of them and just like with themes that means your going to have to use cards that aren't quite as generically strong but in this instance, because they help pull off the really powerful effect of your really rare card, they become useful. So the high rarity card's power was balanced by the fact you had to go through alot of work to play it while people who don't own said rare card can invest their work into making better use of their lower rarity cards. Both the decks with and with out the high rarity cards can thus compete with each other, but the high rarity cards if they work tend to have more flash that makes the win a little more satisfying.
Those examples aren't necessarily the only things that would make me happy but they are examples of things that would.
So yeah, Akjeil pretty much summed up my stance in alot less words. For the record DWildstar, its true I'm not especially happy with lp1 and lp2 cards have the same effect, but as I said before, until I've got more experience with the game I'm not going to make any assumptions about the balance of such things. I'm skeptical but I'm willing to bow before the Japanese players superior experience with the game and trust for now that such a thing is indeed balanced. What DOES make me unhappy is that we have lp2 cards with good skills and lp2 cards with no skills, and theres NO way what soever that THAT is balanced.
The bunnies of Lavato have special abilities, like 'Action Skill: Make Carrot Disappear.'