Why have it rely on some random chance? Instead, make everyone pay a flat percentage of what their gear costs. Right now, there's a 4% chance of an item to break per tick for 7% of the item's cost. Why not just make us pay .0028 (.04*.07) of the item's cost (rounded UP, so no one can take advantage of 0 cost items) every tick? Add it up during the round, then spit out one number at the end: "Your gear repairs for this round cost xxx gold."
This makes it easier to plan what gear you're going to use, and it makes higher cost gear more viable. Instead of throwing on your best weapon/horse/armor/whatever for a single round and praying to the random gods that it doesn't break, you'd be able to say, "Oh, I'm on a x3 multi, I can afford to use this gear, so I'll put it on." This applies especially to heavy cavalry, who I feel are affected the most by this randomness. A mamluk would cost 168 gold per tick, which is 'viable' money-wise at a x4. A single break now costs 4203 gold, which would wipe out 16 ticks at a x5. In theory you have a 52% chance of the horse not breaking for 16 rounds in a row. Obviously, everyone wants to see more variety on the battlefield. This is actually no different from the current system in the long run, it simply removes the random element and makes higher end gear make sense instead of making players worry about breaks.
"What about when someone can't afford upkeep?" you say. Well, instead of the current system, where the item drops an heirloom level (temporarily) until repaired, I suggest that the item simply isn't useable until the repair balance on the item is paid. Perhaps a flat 28% (10 ticks-worth of repairs) of the purchase cost to discourage any kind of potential abuse. Right now, the current system disenfranchises new players, alts, and STFs that don't have a huge sack of gold yet. They want to use decent gear, which in theory might fall under the "sustainable" gear amount, but one bad round and all of a sudden they're in the hole and can't repair their stuff. With this system, if they are under the sustainable amount, they are guaranteed to be able to use their gear, as they will never have repair bills they can't pay.
I'm sure there are a some flaws I've overlooked, feel free to comment, or come up with ideas that might make the system (this one or the current one) better.
tl;dr: Get rid of random chance in upkeep (4% chance to break & 7% repair cost), make people pay a flat upkeep percentage (4%*7% = 0.28%) every tick.
edit: Regarding multiple breaks(thanks RibaldRon):
You are correct about the multiple breaks, I had overlooked that facet of the current system. It could, however, be pretty easily be tweaked by adjusting the repair cost. Say your a round nets you 6 ticks (6:30, 6, 5, 4, 3, 2). The probability of getting more than one break, right now, is about 0.0216 (1 - (.96^6 + 6*.04*.96^5)). In a 4 tick round, it's a 0.0091. For example, using a 30,000 gold build in this hypothetical 6 minute round, you've got an expected value of 410 gold for one break only (the current system), and you're 'saving' 45 gold per round for the value of any extra breaks (11%). For the four tick round, it's 297 & 19 (6.4%). The devs would be able to adjust the repair cost slightly (ie, .0028 to .0025) per tick to compensate. Or, they could give away the first tick free of repair costs, since very little combat happens during the thirty seconds anyway.