Well, if you are looking for opinions and advise, you came to the right place.
I have a number of Leupold scopes, and the TMR is a fine reticle. I use them on my military builds, and hey, Army, Marine and Navy snipers used a 10x scope with TMR reticle and hit real targets.
You have picked two very different scopes. The Mark 8 is very well respected, and a jump from a rather tired line of Leupold scopes when they came out with this a year or two back. I think it is high priced, but it is a great scope. The Mark 5 is a newer scope, and one can debate whether it is an upgraded Mark 4 or a downgraded Mark 6, but all accounts (so far) point to a great value, and a familiar and easy to use platform. Price wise, it is hard to compare the two. The Mark 8 is roughly twice the cost.
I think I wrote a while back that Leupold is like Marriott. You will never find a bad scope (humor me), but, like Marriott, you seldom find a truly great scope. It is hard to pick a scope. It gets very personal. Both in terms of much of the evaluation is subjective, and you will get so many opinions. If you told me that 800 to 1,000 yards was the furthest you would be shooting, I might be comfortable with the Mark 5. At the risk of advocating that you diverge into a universe of questions and possibilities, I would offer that you might not want to limit yourself to Leupold because of their discount. You can get some good discounts from other shops. Maybe not as good, maybe just as good.
A 300 WM allows you to venture out past the horizon, and go further than 800 to 1,000 yards, and as you start to reach, I think I would suggest that you at least entertain a few other scopes. Also, when you think of the TMR reticle, there are others that are very similar, although maybe a little better, in offering the same grid, but with some numbers on it. I am thinking of the NightForce Mil-R, the Steiner SCR and the Schmidt & Bender P4F. Perhaps the Kahles SKMR3 or Vortex EBR, but that is starting to look a bit busy and Hours-like.
I like that you are looking at the 2-25x, generally. That is a good combination for the range and use you are referring to. I think more is too much, and the only possible lower combination is the S&B 3-20x, but the price tag will be very high for an Ultra Short.
Let me bring this back.
-- Personally, I would throw-out the Mark 8 due to price. Not its absolute price, but a price / feature = value matrix. I think you can get more scope for that price.
-- I would add a NightForce ATACR in 5-25x with Mil-R or Mil-C reticle, as this is a really neat scope with a lot of features and great glass. With a $3,000 list price, you can probably get this scope for close to the same price as your mil/LE discount from Leupold.
-- I would add a S&B PMII 5-25 DT P4F reticle. Again, simple reticle, but an improvement over the TMR. You can get one of these scopes for $2,400 +/-, and what the hell, it is Schmidt and Bender. It is not my choice for tactical scopes, but for your use, it might be great.
-- Next, I would add two Steiners: the Military M5Xi 5-25x with either the MSR or MilDot reticle, because it is an outstanding scope, and the price will be in the range of the ATACR. I would add the Tactical T5Xi 5-25x with the SCR reticle. I would add this because it will compete both in terms of features and value with the Mark 5, and the reticle is similar to the NF and the S&B.
Hope this does not complicate too much. In disclosure, I am a new dealer in scopes, and carry a number of lines, which include Leupold, Steiner, NightForce, Schmidt & Bender, Kahles and some higher-end Vortex models, and some purely military / tactical optics.
