Seagullus makes no sense to me.
Loxodon Hammer and Whispersilk Cloak are artifacts, so can be thrown into any deck...But Welkin Tern and Firebreathing are blue and red cards, respectively. So, who plays red and blue in the same deck? I've only seen it once in 15 years of magic playing, and it was basically using blue's card-drawing ability combined with red burn, so the player would need no creatures or artifacts and always have land and fire to deal with anything.
Not to mention, in order for the Seagullus to work as described, Whispersilk Cloak would have to be attached LAST, as attaching it first would render it untargetable for Hammer and Firebreathing. Which means, unless you play Welkin for 1B, Hammer for 3, Firebreathing for R, and Cloak for 3 on the same turn, you have at least one turn to use any means of dispatch on the bird, as it will still have only 1 toughness. So, you would have to 7RB available at once to make it that powerful...if, after nine turns, you don't have something that can deal with a 2/1 flyer before it becomes lethal...well, I don't know what to tell you.
A better combo would be with Suntail Hawk [http://gatherer.wizards.com/Pages/Card/Details.aspx?multiverseid=129753], seeing as it is only W to cast, and is white...which pairs up with red much more nicely than blue. Life gain, cheap and flying creatures, land destruction, AND burn damage?
There are numerous ways across all colors to deal with this pest.
Aether Barrier [http://gatherer.wizards.com/Pages/Card/Details.aspx?multiverseid=22289]
Consuming Vapors [http://gatherer.wizards.com/Pages/Card/Details.aspx?multiverseid=205936]
Gatekeeper of Malakir [http://gatherer.wizards.com/Pages/Card/Details.aspx?multiverseid=185698]
Warren Wierding [http://gatherer.wizards.com/Pages/Card/Details.aspx?multiverseid=152732]
Diabolic Edict [http://gatherer.wizards.com/Pages/Card/Details.aspx?multiverseid=27251]
Twisted Justice [http://gatherer.wizards.com/Pages/Card/Details.aspx?multiverseid=89052]
Hit//Run [http://gatherer.wizards.com/Pages/Card/Details.aspx?multiverseid=107387&part=Hit]
Odds//Ends [http://gatherer.wizards.com/Pages/Card/Details.aspx?multiverseid=107445&part=Ends]
Wing Shards [http://gatherer.wizards.com/Pages/Card/Details.aspx?multiverseid=45835]
Rakdos Riteknife [http://gatherer.wizards.com/Pages/Card/Details.aspx?multiverseid=97119]
Dispense Justice [http://gatherer.wizards.com/Pages/Card/Details.aspx?multiverseid=209015]
You can even use Acidic Dagger [http://gatherer.wizards.com/Pages/Card/Details.aspx?multiverseid=3239] if you ever do get a flyer out that, for some reason, can't kill it. My favorite solution, though, would be Chainer's Edict [http://gatherer.wizards.com/Pages/Card/Details.aspx?multiverseid=29603], seeing as it has buyback. If your opponent has more than one perm on the battlefield, you get more than one shot at it, and it requires 6BBB to cast and buyback, meaning you should be able to pay for casting+buyback the same turn that Seagullus comes out.
Plenty of other solutions, anything that targets the player instead of the creature...such as any of the four cards you illustrated with annihilator...those would work quite well. Also, this one would really piss them off, and have the advantage of being arcane: Dwarven Catapult [http://gatherer.wizards.com/Pages/Card/Details.aspx?multiverseid=159729]...nothin' like a little Fallen Empires to ruin your day, bitches!
Anyway, not trying to be a dick or anything, just could have gotten way more behind this episode if it were based on something truly horrible and seemingly insignificant...like Lab Rats [http://gatherer.wizards.com/Pages/Card/Details.aspx?multiverseid=5178].