Halo: Anniversary - where be I at?

Not that I'm not enjoying this, but how much is left?

Having finally decided to stop playing co-op due to the dumbest net-play
implementation ever invented I tried to slice off another chunk last
night on my own. While I managed that, I'm finding the repeated and
fomulaic skirmishes combined with third regurgitation of the same level
to be a bit of a drag.

We were playing on heroic, so that's how I've decided to continue. I
quite like the challenge of those firefights, but the third time through
the same canyon with the same set of skirmishes smacks of filler rather
than fun.

Maybe I should reveal where I am so that my question may be answered
(clearly going to be spoilers here):

I'm at the bit where you work out that the floating orb thing is
batshit, and that you need to destroy the halo. I've subsequently fought
my way through the canyon twice now and stood in the beams of light
with my specially and newly specifically polarised suit. I'm now
attempting to escape the canyon to get to the pillar of autumn as it
apparently contains a big button that should make the halo go boom,
though cortana has suggested I need to find the captain first.

It feels like I should be closing in on a finale, but if I'm looking at
another few hours of the same old corridors and canyons filled with
giggling circus freaks, I think I might be inclined to take a pass.