1) Since it doesn't look like Hex Channeler from ACG and the Hedge Witch from APG use the same class features (hexes designated) is it POSSIBLE to combine the two of them.
2) If it is possible, then by taking Extra Hex, could I increase the channel dice for it, using Extra Hex?
1) If I'm reading the correct things, Hex Channeler replaces the hex learned at 2nd level, while the Hedge Witch replaces the hexes learned at 4th and 8th. Thus, yes, they are compatable.
2) Channeler says "Every time the hex channeler is able to learn a new hex (including major or grand hexes), she can instead increase her channel energy amount by 1d6."
Extra Hex says "You gain one additional hex. You must meet all of the prerequisites for this hex." with a prerequisite of "Hex class feature."
So long as you already have at least one hex through the Hex class feature, I don't see why the new hex that you learn via the feat can't be used to increase the channel energy amount. However, check with your DM first anyway.
Okay well since I got one answer, I was hoping for more answers.
So how about this: Would this make the witch a better healer than a cleric in terms of being able to spontaneously heal people?
*would like to try to mix up a witch so that she heals awesomely but still can toss out a fireball or two.*
It appears so. By level 20 you could channel 18d6(technically 20d6 max if retraining rules are allowed), which even beats the Aasimar life oracle with fcb abuse, which would be 15d6, granted sacraficing a fcb is a lot less than sacraficing a lot of feats, plus oracles have life link, and are monostatted so probably still end up ahead. But hey, if that's your goal it seems totally doable and as far as I can tell it's legal. Just remember, channeling doesn't scale all that great. Even at 20d6 that's an average of 70 hp's per channel, while mass heal will be knocking out 200, and has the added bonus that it can be offensive at the same time if undead are around.