Haha.

: Didactpire can't just crush Chief with his mind or throw him off
: immediately or even utterly mash him during his first meeting and is

I think it's completely in keeping with the Didact's character and his attitude toward humanity in general. He's impressed by the Chief's tenacity, but he NEVER considered him a threat until he saw him running toward him with a Pulse Grenade. He's a proud character. He probably never thought the Chief would survive him throwing him the way he did when he first met. And I'm sure he never thought the Chief would survive his Cryptum's Slipspace rupture (New Mombasa sure didn't :P). And I'm sure he never thought the Chief would escape on a Ghost. He didn't think he needed to kill him. Granted that's a trope of most villains, but I think it's pretty justifiable here. The Chief's luck got him out of ridiculous situations plenty of times when Bungie was taking the reigns.

: instead content to get beaten by light, space magic, a grenade

You're simplifying things too much, ain't ya? :P

: and the big Composer were never truly a threat, especially considering the
: ease with which they were destroyed.

The Earth was in the middle of getting Composed when you reached the Didact and the Composer. The threat is literally staring you in the face. And the ease in which they were destroyed? What about on the Ark in Halo 3? All the Chief had to do was stroll up, push a button, then watch the Arbiter stab a sick old man. Bam. Universal disaster averted.

: Haha I don't see anything you're saying as hostile.

Well that's good. Maybe I just feel that way because my blood boils sometimes. :P