Firstly, combat dailies do not grant any XP rewards currently. I'd suggest adding XP lamp as a reward for completing one which you can use and choose any combat skill you wish to get xp on.
Experience is granted based on level of course.

Second suggestion is to add ancient effigies. (http://runescape.wikia.com/wiki/Ancient_effigies). You would get these every 5th daily you complete.
There are 4 stages of effigies and each stage has two random choices which you can choose to what skill you want to get xp on (No combat). There are no level requirements to open them like RS3 has.
Effigy will advance one stage each time you choose a skill. 5th stage you'll get a dragonkin lamp which can be used freely to any skill.
Experience you get depends on your level so more xp at higher levels.

Some dailies are hard and can take a lot of effort and time to complete so I think ancient effigies are a nice bonus for doing your daily challenges.

Thirdly, how about thieving and hunter dailies? Construction dailies sound kinda of meh so I think it should be left out. Hunter kind of falls to the same category unless the dailies are simple like some birds and swamp lizards at lower levels, different salamanders and grenwalls at medium/high levels.
Thieving there are bunch of great NPCs you can pickpocket and stalls to steal from so that could definitely be added.