is the fel guard worth it, and how well si the damage and how well can it jold aggro, is it good for soling instances?

Personally I find that if you have just hit that magic 50 you want to stick with your voidwalker. But once you've leveled enough to arm your felguard with a few spells he starts showing potential. But if you ever go into a instance people are still gonna ask you to get your imp out! :P

Another thing to note is Felguard has 1/3 less health than voidwalker which at lvl 50 is about 1k of tank down the drain.

fel guard is pretty good though it seems a bit weak if you get him as soon as possible because he won't have all the skill that make him useful.
mine levelled me nicely from 60-70, what instances are you hoping to solo?

scarlet monstery, armory/cathedral

Why does it matter if his health is less?

I'd rather have more mitigation instead.

EDIT: Personally, I hate the FG. Worst spec ever IMO. No Devour, Spell Lock, CoEx, Siphon Life really sucks a lot.

the FG is pretty good.  i had him from 50-53 but then i got tired of him because of the low health.  My voidwalker had more survivability and with soul link active he still lasted a long time.  the VW doesn't push the damage like the FG but he does have pretty good aggro with his torment and the other one, forgot atm.  but i would stick with the VW till 60.

Fearyourazz
Madoran

i have used my fg since lvl 50 I am 62 atm. I use him all the time I tried using my vw and he doesn't hold aggro. My fg kicks ass I send in my fg dot the sucker and do a few sb and he is down.... ZI heal him and we are good to go.

Caslar lvl 62 human lock
Unkown Gods
Arathor

but you always have to remember to heal the FG and if you get ganked by like 3 or 4 mobs then you're toast.  he gets creamed and you can't health funnel cause you're gettin hit too, so you put him on the mob attacking you and his health keeps dropping, you bandage, and health funnel but you can't get his health over 300 cause you're bein ganked.  plus since you're spamming HF, when you do get slapped your health is half of what it was. boom, toasted

because of this, i use the VW for questing and grinding, personally i think he holds great aggro with his taunt and torment. he may not do the damage but that's what dots plus instant shadow bolts are for (nightfall, get it, it's definitely a keeper). 

yeah so, given all that, VW ftw.

Arkoss
Madoran

If you make your FG attack the mobs you are fighting then they won't interrupt you.

Yes healing causes threat but if you alternate the FG then it can hold aggro.

Even against 5 people at once.

ya I agree with the above poster. But the only thing that I try to do is look to see which mobs to go after first. I usually dot them and hope that only one mob is aggro'd. But I love my fg and don't care if his health is only 1/3. he does a great job. And you should wait till you can get some spells for him it doesn't take long. I started using him when I first got to 50 to do ZF in tanaris and we did a great job...

Caslar lvl 62 Human lock
Unknown Gods
Arathor

Dang, all you people that hate the fel guard are crazy.  He holds aggro much better from the get go and his lower health is countered by more than double armor.  He also does much more damage.

For soloing instances? Well you want the voidy, but only because you will be able to kill more without eating as much.

Once the FG has charge they are awesome. Yes you have to HF more but the damage output and the stun are great tradeoffs.

At 57, charge stun spam has let me kill players two levels above me, if I got the drop on them. Between charge, death coil, fear and howl, it's hard for them to hit you.

And once you get instant corruption its all gravy.

As was said above, though, with a group in an instance, plan on playing your imp a lot....heh. 

Just two levels above?  At level 52 I was able to take out 4 level 56 mobs.  Of course, there is a fair bit of HF and reapplying dots but it's possible.

im talking about *players* not mobs, see quote

if you're going to use the VW then you definitely have to spare 3 points for improved VW so that he does a bit more damage, thus holding better aggro.