The patent troll problem can be solved industry-wide with the formation of a patent-troll legal defense fund. A bunch of companies put money into a fund. If any company (not just the contributors) is sued by a troll, they can apply to the fund to pay for legal assistance (applicable controls can include approval, fund limits, etc).

If trolls see that companies are more likely to stand and fight, the cost of trolling goes up and the rewards become much less predictable. Hence, trolls will lose their ability to raise funding to purchase patents and have less troll-surface-area to act upon. This will lead to a vicious (virtuous?) cycle for the troll industry.