It's not less acres. If you're dicing, it's the same amount of acres. 125 acres/hour for 24 hours = 3k acres/day, approximately what you get from dice+explore now. If you war, those acres continue to pile up (or get used, if hits are big enough) at 3k/day whereas currently you would only get 480/day in pool growth.
I admit, I am unsure all the ways this could shake out and the new strategies devised. The reason cows are so powerful these days is that it's a cheap way to use your pool and leaves you with a topfeeding core. But bio has shown that if you use your pool elsewhere you can do just as well, with a nigh-untouchable core (compare bio and sanc kds now...sanc with the cow would have no chance head-to-head). The reason cows are preferred is that non-cow kingdoms find it very hard to use their pool, without tons of cf's. The proposed changes make it easier to use that pool. Even so, I anticipate different strategies being run, with balanced-core or multi-cow setups possible. I do not know which would prevail. And while cow kingdoms might prefer to put all 30 acres/hour on their 4 cows, the non-cow kingdom that waves them will have exactly the opposite inclination.
The key in the explore cost formula is that it does not blindly make exploration harder at bigger sizes, the way this age has done. This age doubled explore costs at 2k acres compared to last age - making it extremely hard for core provinces to explore in any top kingdom. By relaxing the size limitation as the age goes on, cows are made possible but expensive. Still, if it's felt that cows might be overpowered - simply increasing the scaling of explore costs will help that (i.e, square that multiplier).
Oh, and as for your fourth point - that is extremely wrong. At 2k acres later age, explore costs would be significantly reduced and exploring would be much cheaper than dicing. It would be quite easy, after a war, to double your chained provinces up from 2k to 4k. This is something that cow kingdoms have always had to give up, to their cost - except for this age, where it was too expensive for anyone to do.