Posted 17 February 2011 - 10:09 PM
After an extensive 5 minute search, all I've found is
On the bottom-left of the magic spellbook interface is an icon that looks like a shield. This shield represents 'defensive casting'. If you click this button, you will gain Defence experience whenever you cast combat spells, at the cost of receiving a reduced amount of Magic experience. To return to casting your spells normally, simply click the button again.
That's pretty much all there is about defensive casting on the Runescape Website or any fansites/databases. I guess until further evidence, anything we say is speculation.
Edited by Funny Bunny, 17 February 2011 - 10:15 PM.
My natural tendency would be to say that there is some sort of downside in terms of offensive potential. I don't really allow myself to train defense on my account but I do know that almost every controlled/mixed combat attack style is less potent than more aggressive counterparts. Take for example defensive mode for ranged. While it provides more blocking potential and defense xp, it is slower and/or less accurate than other attack styles. No, I'm not claiming that defensive mode will cause your max hit to decrease because these are fixed based on gear and spell, of course, however, I believe jagex would somehow balance the system and maybe increase your ability to defend with that option selected while decreasing your accuracy. It'd be really hard to tell and quite frankly I think any difference would be marginal. For now consider this an extended "maybe" while browse the rs manual for more info.