Some time ago we had new magic systems with different tiers of magic _bound_ to spell scrolls. It sounds good and necessory in some cases - for example players may use more 'weak', previous Tier of some spells in addition to more powerful ones sometimes ('Toxic Moisture' spell - to prevent crushing potions on the floor) but...
...Previous system was very much easier in terms of spells managment. Currently there are a some of problems in terms of usability:
1) When you 'order' spells you never know how much skill do you need for certain tier of spell. Example: I got 25 sorcery and got 'Manathrust I' spell in my spellbook. I've no idea - do I need 'Manathrust II' or 'Manathrust III'. So I have to order it just ot check - do I have enough skill for it or now. And now imagine, that one of your books was destroyed and now you need to 'test' which tier you need to buy _again_.
2) You need to order loads of different tiers for the same spells... Its kinda VERY boring stuff to do - managing loads of spells with different tiers. Its like having 3 OS at your desktop - Windows, Linux and OSX - and trying to work at them all at the same moment. Not fun.
3) It just very confusing to have so much different tiers and watch for them to be up-to-date...
Conclusion of my impressions:
Istar - its very fun class to play... has to be. But currently managing of this class makes it worse for me. Previous system (without tiers bound to books) was much more comfortable to play.
Possible solution:
1) I suppose _in most cases_ it would be fun to make spells tiers bound to magic skill, not to spell scrolls (except Toxic Moisture and some other different effect spells).
For example:
You buy spell scroll of Manathrust. At skill 20 it starts to work as Manathrust II. At skill 40 it become Manathrust III & etc...
This post sponsored by Occam's razor:
entities should not be multiplied beyond necessity
Occam also said:
We just don't need a tiers for a lot of spells. Why do we need different tiers of 'Manathrust'? Ok, 'Toxic moisture' has different effects with different tiers, but most of spells - don't. Why to make more complex what could be simple?