I would rank an Average Champion with score of 3 out of 5.
I would rank Tainix with score of 3.5 out of 5.
This is why players generally don't use her in alot of area's.
Their is alot of better options vs. Tainix in the grand scheme of things.
Tainix gets mainly used in Faction Wars.
Tainix healing competitions isn't has high as her.
- Abyssal is a 3 at healing
- Fellhound is a 3 at healing
- Vilespawn is a 2 at healing
If you have 60k HP on Tainix, She can do 1,800 Heal per hit.
Keep in mind, She hits twice so it be around 3,600 Heal.
If you add Masteries, you could jump to 4k Heal most likely.
Sycl of Drakes does a 10% heal based on allies HP.
Most generic Nuking hero's will have HP amount of 30k - 40k.
If you think about it, Sycl heal will be around 3k - 4k.
The Healing Tainix does is certainly on par with Sycl.
Some might even say Tainix healing is better vs. Sycl.
The problem is you have to jump thru a bunch of hoops.
Tainix has a bunch of restriction which need to be met in order to heal.
Sycl has no restrictions - She only needs to take a turn which is easy to do.
Obviously, we can argue about Tainix all day long.
Some can say you should build her.
Some can say you shouldn't build her.
Both sides will most likely have Valid Arguments.
In the end, it will come down to what you want to do.