Well I guess I'll break this down for you a little bit easier. I know the rates are 98% or 96% and not compounding, but you also have to take that into consideration when doing it.
If you want to take a skill from +0 to +5 and it starts at 98% and decreases 2% every + until +5. Thats 98,96,94,92,90. So final is 90% chance to succeed. Compounding means you have .98*.96*.94*.92*.90= 73.2243456% chance of going from +1 to +5. That's much different than just 90%.
I wanna say I feel your pain, but try enchanting things going +5 that ALL have less than 50% chance, then tell me what the real pain is. Top Circlets are 50%, 45%, 40%, 30%, 15% to +5, with a staggering compound of 0.405% chance to go from +1 to +5, yet there are lots of +5's.
Just kinda sucks.