Take everything I said below about John Lackey and reverse it and you will come close to assembling the Rich Harden package. As mentioned, Harden made the exact same amount of starts (51) the past two seasons as Lackey did. Harden did throw noticeably fewer innings in that span, 290 to Lackey's 340, mainly as a result of a difference in approach. Lackey averaged 3.64 pitches per plate appearance the last two seasons, Harden was at 4.11. Strikeouts generally take more pitches to complete so it should come as little surprise to see the difference there. The important thing is note is that Lackey threw a total of 228 more pitches than Harden over 2008-9, the equivalent of one extra start per season.
Unlike Lackey, Harden's swinging strike rate is less trendy, partially due to the lack of data points in 2006-7. However, Harden had established a 11% rate in 2003-5 and was at 15% both of the prior two seasons. He would probably demolish Texas' hitters. Harden is also going to walk a good number of fellows. Interestingly enough, Harden's tendency to throw strikes is no worse than Lackey's, both hitting the zone about half the time. Harden is much more often to throw that first pitch for a ball though, but again, that's part of the deal with high strikeout pitchers.
Harden is also more of a fly ball pitcher than Lackey. Again, Harden is about the strikeouts so pitching up in the zone is part of that most of the time. All of this combines to give us the overall picture of Harden to Lackey, way more strikeouts, a few more walks and a few more fly balls. While Lackey's tRA* floated around 4.4, Harden's is around 4.1 though that came in a less offensive league. The difference between the two in terms of those figures is negligible. CHONE is slightly more bearish, also projecting Harden to be equal to Lackey in performance level, but Lackey's clear inferior in durability.
Even accounting for Harden's higher catastrophic injury risk, he grades out as being worth $12 million or so per year. To compare them directly, Harden's fair value over a four year deal would likely be around 4/44 compared to Lackey's 4/52. That Harden's health knocked that 4/44 down to 1/7.5 with an $11.5 million option is what made him a great target. An opportunity potentially (we don't know what went on, there may have been nothing reasonable Jack Z could have done) missed here and that the Rangers signed him makes it all the more painful.