i know fire has more powerful imbue, and can be secondary nuke, it is not really necessary to have.
1) although fire can be a secondary nuke, but by level 70, you will get another light nuke making it 3. the 2nd book is good enough to be your secondary while the 3rd can be your primary.
2) if you do not get ice, you are basically killing yourself right there. because glavies can crit well over 10k with mars, triple stun, boom you are dead. mana shield should be used by all hybrid int/pure int.
3) light also have int mag buff, parry buff, parry passive. ice has phy def+ buff, phy def passive, and another aoe nuke. which is great when leveling. use light nuke -> ice 2nd book. = mass aoe mob killing. fastest exp
4) if you do 80 fire 80 light 70 Ice 70 Sword, u will be weaksawce for 90 cap and 100 cap.
light nukes > fire nuke
light mag% buff > fire flame body
light grasswalk > fire
light parry > flame body
ice mana shield > stealth detector (in fire series)
the only reason to get fire is for immunity. but i would still get ice over it.
also u might wanna check up on that link below
http://www.silkroadforums.com/viewtopic ... sc&start=0