How often do you get to use Dragon Mage ? He looks like he costs a lot and still has a chance to not trigger...

I don't see him very often because I don't have any tutors, but he has been useful in the past. Sometimes I'll end up wheeling him away and sometimes I need a beatstick.

In my playgroup, usually somebody will be without a blocker, so getting him to connect isn't the issue.

I'm open to suggestions on what could replace him, though.

Well, in the theme of dragons there's Spellbound Dragon and Knollspine Dragon the first isn't nearly as good, but might stay around longer just because he doesn't threaten as much... the second costs the same, but you can get immediate effect out of him (meaning he might stay around longer after the first use...) and you can often draw a lot more at once with him in a massive EDH game.

Arcanis the Omnipotent is a pretty similar cost, but he has the advantage of a built-in bounce, and controlled uses... (not to mention he plays REALLY well with Mind Over Matter )

The dragons won't be very useful. Spellbound Dragon would only be a beatstick. All of my damage comes from wheels, the minimum of which is 3 CMC so I would need 10+ mana to get any value from Knollspine Dragon . There's so much more I could do with that mana, like Jin-Gitaxias, Core Augur .

Arcanis the Omnipotent is something I've been considering, but I think he'd be a big target and won't last until I untap. I'll keep him in mind, though.

Makes sense. Yeah, Arcanis the Omnipotent is a pretty big target, but one of the best things about him is that built-in bounce...

Another slightly less conspicuous utility guy is Mercurial Chemister who can often sit around drawing a couple cards, or pitch something massive to make a one-cost burn spell. (though this works best with something like Illusionist's Bracers attached to him)

Or perhaps some removal? It's hard to take out enchantments in Grixis, so maybe a Spine of Ish Sah or a Argentum Armor to take care of those game-ending enchantments... yeah, they cost a lot, but they're fairly valuable for Grixis.

Arcanis can protect himself, but it's a huge investment. I'd need 10 mana (there's that 10 again...) to be able to cast him with protection.

Enchantments aren't that big of a deal in my meta so I don't think I have to worry about dedicating slots for removal.

Then perhaps something like Black Sun's Zenith , Life's Finale , Damnation , Decree of Pain , Bane of the Living , Toxic Deluge , Plague Wind . after all, you don't appear to have much in the way of field-wiping capabilities and there are often times where flipping tables and destroying everything is perfectly acceptable... (also Jokulhaups could be amusing... not very good for you, but amusing)

Damnation is good, quite pricey, but low CMC... I'm quite fond of Decree of Pain , though if there's a lot of creatures there is the possibility of decking yourself out (though with a Psychosis Crawler that could win the game...

Decree of Pain would have better synergy, but, again, I can usually win the game with 8 mana.

I'm not too worried about the price of Damnation because my playgroup allows the use of proxies of cards worth under $50. Damnation hasn't hit that mark....yet.