Would you like to play against any deck containing the combination of cards below?
6 Devourers + 6 Pest
6 Steal + 6 Improved Steal
6 Reverse Time + 6 Rewind
6 Sundial + 6 Upgraded Sundial
6 Phase Dragons + 6 Elite Phase Dragons
6 Dimensional Shield + 6 Phase Shield
6 Empathic Bond + 6 Feral Bond.
6 Poison + 6 Deadly Poison
6 Deflagaration + 6 Explosion
6 Immolation + 6 Cremation
These are only a few of the killer combos if you allowed both basic and upgraded cards to be played together. Some of the combos more broken than others (Pest+Devourers guarantees your opponent having 0 quantum at all times.) and some combos is just plain difficult to break (Dimension Shield+Phase Shield=36 Turns of Invulnerability, Sundials+Sundials=ATLEAST 12 turns of invincibility, with a potential 24 turns if the bug is fixed.)