Well I thought it was a little slow, but not what I'd call quite slow. I have a fair few rifles and I basically look for something different from each one. Yes there are the charecteristics such as weight, length of barrel etc, but from my spread of cartridges, it would be easy to make several of them perform very very similarly. I could stick a 100 grainer in two different .243s and the 25-06 and throw them out at the same speed. Isn't that just like having 3 x .243? YEs the BCs are different, but in the field, come on, really? So what I was after with my 25 was a touch more weight, a touch more speed for some of the areas where I shoot that literally has no cover so 300 yard shots were quite common. Of course the .243 will do that. Of course the 7mm will do that, but where the fun in that? Is there one cartride that will do everything you want in the UK, of course. There are several. But personally, I don't want just one rifle. IN the very beginning, I sent 8 handguns to the furnace and swapped the vacant slots for 8 rifles.
So, is your 25 too slow? I don't think so. I'd need to look at the charts but it's probably a smidge more than a .243 For most shots it's probably as good as you'll ever need. But it is kinda bottom end of the book