My husband is 6'5" and really cannot fit in coach. However, we have a new take on all of this. For SE Asia, we did a direct flight from IAH to Tokyo and then on to Ho Chi Minh. We got an incredible price in economy on ANA and I took it and prepared to be miserable! However, since the flights were pretty direct, it was not bad at all. In fact, we were pretty comfortable because we were not traveling that long. My new theory is to pay a bit extra for direct flights or even drive to Dallas or Houston (we live in Austin) to avoid as many connecting flights as possible.
My dad, on the other had, had Business Class on the way back from SE Asia but had a 10 hour lay over in Osaka (only flights he could get with miles and he is AA Platinum!). He said it was miserable and not worth the extra miles (even though Business Class was nice).
For Australia, I plan to fly direct from LAX to Melbourne for some pre-days and back into LAX on the return from Brisbane. We may spend the night in LA and then fly direct back to AUS. If you are like us and can't afford the business/first splurge often (even with all my credit card tricks and bargain hunting), book the shorter flights (even if they are more expensive)! It's not as comfy but makes it a lot more bearable!
And calypso, my son is the diva (it's a NIGHTMARE!). Every time we board, he asks LOUDLY, "Are we in First Class?" We are having lots of conversations about entitlement and first world problems. However, I can't deny that the kid has good taste!