The Orb of Health (hope I got the name right) is the item that restores a massive amount of HP and mana over a few seconds, unless you're damaged.

Shield is Oak's ability that prevents you from being damaged for a few seconds.

So, I thought to myself: "I wonder whether the orb's check is applied before or after the shield negates the damage?"  I tried it out in-game, and sure enough, I can sit there in the middle of the enemy fortress watching my health and mana bars zip up!

I have mixed feelings on this.  On the one hand, giving one character the ability to get a massive HP/MP boost (around 3000 IIRC) every 30 seconds or so feels unfair.  On the other hand: the item costs 4000+ gold, you need a few skill points in Shield to use it with impunity, this makes the Shield skill (which I otherwise never took) more valuable, and using Shield this way means it's not available when you see the Torchbearer winding up with a fireball spell.  Even with this advantage, I got killed a few times when I was careless and walked too far into the enemy fortress; if they're damaging you enough to kill you quickly, this combo won't help.  It's mainly useful for holding off a slow drain from the fortifications/minions/creeps and/or low-level demigods.  Which seems just like what the item is intended for.  Also, while the warpstone isn't 100% effective, you can use it to do the same sort of trick (warp out of battle, activate the orb, run to stay out of battle until you're healed).

Anyway, just wanted to make sure that this was intended behavior and not an oversight.