thanks gya.. i always have the idea that KE isn't possible as a main tank. been bringing cass along with me all along since beginning as she's my LI. wondering how can i tank effectively with KE now if i'm not bringing in cass. i always have varric and another mage along. so the replacement obviously going to be sera.. i was planning her for my 2nd PT though. guess to tank with KE effectively.. i need gear that can generate threat plus guard. all these while i have been feeling the pain of a tank beside my KE as i played with FF. i'll try to ditch cass out and replace with Sera this time.
any suggestion on the item/gear/accessories? i think for crafting i may need to go guard generation. something with mana regen will be great since i can immo spam and hopefully put up some fire mines. but for tanking will it better to forego firemine and go ice instead? for that 50% damage reduction on ice armor. thanks for any insights.
Hm, you could try something like this: Knight Enchanter Build
Ideally, it would be nice to take rejuvenating barrier, but unfortunately you have to get peaceful aura first, which is counter-intuitive if you want to hold aggro.
Spirit blade is only there to lower cooldowns via clean burn. And for stripping guard, I guess. You can quickly charge it very easily with energy barrage.
Fade step is great as a way of closing distance and generating a bit of barrier at the start of a fight in case your other mage misses you with barrier.
If you're set on keeping immolate, you could switch it for fire wall, but I think there's something to be said for dropping a static cage, panicking the enemies inside it, and watching them try to leave only to get zapped back onto your fire mines 
For gear, the Andraste's sacrifice has a useful chance to taunt enemies, as well as improving mana regen and decreasing cooldowns. Your other main method of generating threat is to charge in and spike damage to grab as much aggro as possible. The ring of doubt is great for auto-crits, but going into stealth will drop threat, so you could just stack critical damage instead.
A pact belt of your choice is also a good idea. Perhaps storm pact with an electric staff?
For masterworks, heal on hit is always great with energy barrage. And walking bomb, the damage is beautiful if it procs from a fire mine, winter's ruin or fade cloak.
You won't need guard on hit once you have fade shield, you'll basically always have barrier, even with barrier breaking promoted enemies, you'll constantly be pouring out damage so your barrier will constantly be up. The only exceptions are in JoH and Trespasser, which is where fade cloak is again handy. Plus, the 1000% spirit damage will immediately fill your barrier again. Also, you can mash spirit blade a few times as well, when it's fully charged it will generate a nice chunk of barrier.
You're right that a KE wont tank as effectively as a warrior since you lack proper taunts, but you will be able to hold aggro pretty well by putting out enough damage.