April may be cutting it a bit fine, and I doubt whether any "sales" will be on that close to peak season, however as everyone suggests, it's impossible to predict when "sale fares" will be available.
July is peak, peak, peak.
As Vada has suggested, have a good look at Webjet and skyscanner to get an idea on what's around.
We did that recently, and managed to score a great deal from KL to Paris & Return on the new Malaysian A380 service middle of June, returning end July. Then grabbed an Air Asia flight Sydney - KL with an over night each way (our choice), all up AUD $1450 including all taxes and bags. That was as a result of monitoring skyscanner for a couple of weeks, saw the deal with Malaysian and jumped on it.
I know we are not travelling on one ticket with that added security, but figure an o/n in KL each way is a nice way to break up the trip and get our Asian food hit at the same time!
Otherwise, if you're not confident, go visit a TA and pay the small amount of commission to feel safe.
If I were you, I'd probably try and confirm your dates soon and get cracking.