The 2p and 4p will add a considerable amount of healing but it comes down to how well you are at using riptide and how often you cast chain heal. You need to cast chain heal quite often to proc the additional riptides and use riptide itself on cd to benefit from the 25% increased crit chance.
Looking at some of my own logs it contributes (a rough estimate) anywhere between 5-8% of my healing. It will add some mana from resurgence through the increased critical chance of Riptide on top of that.
The drop in raw stats, well I am not a big theorycrafter but assuming I have done this correctly, the loss in intellect should be ~4.3% decrease to raw healing if swapping to HC tier pieces. The stat transition from mastery and haste to multistrike and crit will account for further decrease of ~1% maybe more.
There won’t be a huge difference if looking for pure output. I think it’s up to you if you want to try and replace items and test it out, but if you had HC tier upgraded it would be worth swapping.