I already considered that. Tell me one situation where Ice Shot (chilled ground) + CoH + Temporal Chains isn't better than Burning Arrow (tar effect) + CoH + Temporal Chains for support builds, PA builds or bow builds.
The fact is that chilled ground + Tempoaral Chains is already "strong enough" in slowing down enemies movement speed that the difference between 30% and 50% isn't that much. Chilled ground even slows down cast and attack speed which reduces the damage potential of mobs greatly and make your charcter and your group more safe. so chilled ground > tar in every scenario i can think off (except monsters are immune to chill, which is only Atziri at this time and there movementspeed reduction doesn't matter at all since she doesn't move that much)
Chilled ground + tar + Temporal Chains + Abyssal Cry + Wither would result in a extreme movementspeed reduction which makes the mob almost freeze in place, but i don't think it would be practical or efficiant enough to play with. I rather shoot another Arrow for PA clouds or create more burning ground etc. because it is easy to do and faster.
I wouldn't even go as far as trying to place one above the other. They rather have different purposes:
For a support build, that can actually afford (regarding the time spent) to use a Ice Shot + CoH combo all the time, I doubt Burning Arrow would be a worthwile alternative.
But now think of a damage-oriented build that utilizes Burning Arrow to spread burning ground with capable ignites. Occasionally not igniting an enemy will lead to tar on ground which then keeps the enemies in the (prior to that spawned) burning ground for longer. (The low chance of that happening on the jewel probably needs some attention...)
Sure you could argue that apples > bread in most cases. But why would you use apples, when your intention was to make a sandwich?