The 2/5/10/15% learning speed cards are not all that useful. I started this alt with just BL5 in advance of iMG being released, and have pretty much every useful skill -- without ever buying the speed cards. Tank cards, multiplier cards, and raw capacity cards have always been a better buy.
My idea is to make the learning speed cards work like the quoin cards - instead of a cost reduction, as a speed multiplier. This would give a greater sense of accomplishment to work ones way up to 7x etc. Skills would need to be rebalanced to suit -- make [highest level skills] 6x longer and you end up in the same place at max (15% faster), but now the speed cards would have real meaning (7x faster than base). Mid level skills would get a smaller bump (e.g. a smooth exponential curve), lowest level skills would stay where they are (e.g. AK1 would not change, AK2 would go up 50%, AK3 would go up 2x...)