You know the rules are more or less abstract. Having weapons codified in bands of reach keeps things simple. I have seen systems (both wargaming and RPGs) that use individual weapon reach in feet and inches, and it gets really messy - more over, the ones that account for individual arm reach! But I see the rules should be a balance between abstract and realism, and more over - be open to houseruling. If you want to keep to the abstract rule (medium-size reach: 5', 10' for reach weapons), then keep doing so. If you want a more tactical approach to reach, then adjust things until you are content. I personally like giving pikes and other pole-arms better reach then 10', as that seems a little to short to me. 15 to 20 feet sounds like a good range.
A thing to consider with pike weapons, is that its best used in tight formation, at least 2 ranks deep (3 or more being ideal), and braced for a calvary-charge - its like a wall of spikes! Outside of using them to defend a besieged wall, pikes - and other pole-arm for that matter - are terrible personal weapons. They are too unwieldy to use effectively like a spear, are useless once parried, and a bitch to use in close-quarters (unless it breaks, then you have an improvised quarterstaff).