ok, first of all, who said this was a defensive team? it's a balanced team. jiraichi's a sweeper, dugtrio's a revenge killer, heatran and zapdos are bulky sweepers. theres also no residual damage on this team, so i really can't see how this is a defensive team.
All six of the pokemon are defensively eved, none of them have any way to stat up save for Jirachi (which is the offensive centerpiece of the team, granted, but still)
how is this team stealth rock weak? 3 steels my friend, 3 steels.
Take Heatran out of the equation, it's neutral.
But I'm speaking to Spikes more than Stealth Rock; a team that
1: is mostly defensive
2: it's main form of offense is setup
3: is 4/6th ground based
cannot afford to be taking 12-25% damage a turn, especially since you will be switching in and out a lot until you can get Jirachi going. I am of course speaking of a situation in which there is only one layer of Spikes down and Stealth Rock.
SD Life Orb Weavile? Not really, seeing that Jirachi is 2HKOed. CB Weavile is more prediction-reliant but one mis-prediction (i.e bringing Heatran in on an expected Night Slash and taking a Brick Break in the groin and CB Weavile becomes much more of a threat, seeing that Heatran's your only safe switch to it. Of course, Duggy can revenge CB Weavile any time it wants (but LO Weavile can Ice Shard obviously).
I'm thinking about Donphan, as it isn't ohkod by a life orb sd close combat.
Yes, that would solve your problems right there - take out Bronzong (which honestly doesn't add much to your team besides sleep), and lead Zapdos.
As for Magnezone, here's your problem - there's no way Magnezone is going to kill your steel without Magnet Rising first. Which means you're probably not getting that Duggy revenge kill, especially if its a Subbing Magnet Riser.
I said I wasn't overly impressed, not because it's not a good team, (it is, and I can see how a good player can win with it) but because on paper, it seemed to have a few weaknesses that could be exploited by skilled players (in short, it's not an almost-perfect 99.6% coverage-type team in my view). Even the threats I mentioned are not an absolute kill situation for you; if you outplay them, then you can get around it easily.