Greater symbol of magic increase your spellcraft percentage. And spellcraft don't affect crushing hand spell at all as I remember. Even if it affects, it does not affect chance of stunning.
I remember as I fought invoker with Ajraah. He had 30 saves at row, but anyway he got four or five permastunning hands. Noone in this mud have such stunning skills/spells that gives caster lag of 1 and gives victim same or even 1.5 round lag.
about 4 stunning effect - it's just my luck (and your unluck)
if you look previous log - seems probability nearly 2/3
about Symbol - agreed. spellcraft doesn't affect checks on several spells (seems on all from books, except imp magic missile)
but if we take a look on sting of manticore and hold person - it's HOLDS more effectively (but checks fortitude saves). so if crushing hand need modifying - only in checking saves. should invoker have something holding or not ?
(btw 60 mana per casting also quite good price for such thing)
i can damage (you call it spamming c 'enh fireball' or c sheet) or hold (crushing) while fighter could deal damage and hold (especially with drum)
at least i don't suppose that everything should be fixed after lucky kill
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