The problem is that in all the set, all sphere only focus on the set even and even, as the file space is only 25 cards...if i insert all 3 in the file, 9 sets will be the maximum number.
A standard big gowen: 3 bringer, 3 alliend, 3 bof, 3 file arrow, 3 roar, 3 sakura and other cards...
While every set you get a new damage card, you either switch out the old, less useful card or just ignore it...as they serve for the same purpose.
Say dragon breath, fireball breath...
They are just quite similar.
Falkow return series:
Tidalwave, return, wrath of sea lord, disjunction, withdraw starg., cyclone, waterspount, wizard's gale (Total 8 of them in 10 set, similar to have at least 1 in each set)
and i think one day, there may be a grim that will return target lv 6 unit or below and is a lv 6 falkow grim...(don't let me get right please...)
The Development Team must know which sphere can have or must not have:
For example, Lawita will never has a unit that gen. SP without sac. itself
Falkow never get revive falkow unit grim, etc
There should be some cards that have cross-sphere function:
For example, aurora(refess like), gen. SP series, wrath of cons.(lawita-like), though actually they share one similarity, and tempest(gowen-like) hurts both side. (Though, they are not too efficient usually.)
While i think refess can be the trade of all jack sphere where it gets all the choices, but it is not efficient than other sphere...however, when you battle refess, you need to risk yourself as you don't like what the refess 's player will pack in his file.