I have to agree with
@Stonecutter. There are two ways to run temple guard, horde style or small bunker. Without being a horde, the TG lose too many attacks to go head on against most units. So if you want your TG to be good in combat you need a horde. The small bunker is just to keep the slann safe and maybe support our other units.
On the topic of warriors of chaos, I find that TG are about equal for less cost (however, I have only played against tzeench and khorne Warriors). The only difference between them is WS and I. I have two examples.
1. A horde of 40 tzeench Warriors (3+ armor 5+ ward) charge my 50 strong TG horde with a light slann. I lose first combat by about 3 and hold. Second round I have phas protection so -1 to hit and win combat by about 5-6 but warriors manage to hold. 3rd round I win by 1-2 with no buffs, Warriors hold. Round 4, I get speed of light, 10WS 10I, and straight up massacre the Warriors causing them to break on double 1s. I still had around 25ish TG in the end.
2. A horde of 60 TG with a beasts slann gets charged by 30 khorne Warriors and 15 khorne Knights. I get wyssans and curse off and Win combat, the Warriors held but the Knights fled. Next round I get flanked by Belakor and hit by withering and take a real beating. The chaos Knights charge back in but withering is gone and I have wyssans. I win combat but nobody breaks. The only thing left standing at the end of that combat was 4 Warriors and a very wounded Belakor. (I played this game about a year ago so my memory is hazy).
IMO temple guard are extremely good for their cost, especially with a slann.