I've been playing Dhlasim the last few days and have been having alot of fun with him, but find I get completly destroyed online when I come across a competent Adon or Abel.
 
I understand these are bad matchups for dhalsim, but I was wondering if anyone had any suggestions as good tactics. Specifically I have alot of trouble dealing with Abel's wheelkick,  adon's jaguar tooth and jaguar kick.

I'll trade you info. Tell me how to deal with Slim as an Abel LOL.

Sim/Abel is pretty awful for Sim once Abel is in. You're going to want to try to keep your button pressing in that match almost totally reactionary if you can help it, because one roll/jump through/over a stand fierce and Abel will get in and beat the fucking shit out of you. Tips for dealing with wheel kick: wheel kick's startup is both slow and vulnerable, so if you suspect one, you can walk up slightly and react to it with stand forward or stand strong to ping it out of the air before it even gets going. Wheel kick is also varying degrees of unsafe if anything other than the tip of Abel's heel touches you. If you block the top of his leg he's going to be between -10 and -12 and pushed right into your face, so you can punish with yoga flame/super combos from back + forward kick, etc. Even if wheel kick hits you from point blank, he's still at -5, so you at least get a throw and escape. In short, hit wheel kick with an upward-angled poke as it starts up, and learn to tell which ones are unsafe so you can punish if you block it. 
 
EX wheel kick is way faster and blows through fireballs, so you kind of have to worry about that too. The same general strategy applies; just watch your spacing, know your poke ranges, and use them to hit wheel kick on reaction. 
 
You can keep Abel out fairly well using that as a guideline. Rolls have recovery at the end, so tag those on reaction with stand fierce or a close normal into yoga flame. His jump-in attacks all lose to different Sim buttons: his jump forward kick loses to Sim back + roundhouse knee from long range, and back + strong from closer. His early jump jab has a weird hitbox and will counterhit your AA buttons at seemingly random times, so make sure you time your AAs well. If he tries to dash in, you can easily poke him. If he focus absorbs a long poke, use another fast poke afterwards and eat his grey damage.  
 
Once he gets ultra, you can't throw fireballs and he's going to try to push you to the corner and bully his way in. Stick to the same gameplan if it's been working, but you'll probably have to play it a little loose and make some reads. If he touches you with step kick, stay calm and don't mash, then just make an escape guess or block. Slide out of the corner works well if he tries to cross you up, followed by an instant air teleport back out of that bitch. 
 
Good luck, because that shit ain't easy.

Cross up fireballs yo, only way to go