Also…when PCs are behind cover so you make it hard to hit them…perfectly fine…have a large troop of the enemy flank them…throw a D6 timer on them, let them know they see a large group running off to the side…if they hit on a perception roll, they are armed with bows and short swords, there might be 10 of them.
Now if monsters are behind cover… they are hard to hit…if only enemy, up the TN by 2~9 to account for the cover, if the cover is overcome, lower the TN.
If some are behind cover, and some are not…then use hard.
If a player misses on a hard roll, next roll is normal, if misses again, next roll is easy, as long as they are doing the same thing…timing the guy, as he pops out for a second, adjusting to hit that small hole in the armor under the shoulder…getting the enemy paladin to lower his shield just so…
After the hit…it all resets. If the PC does a different action, moves back 20 paces then shoots…it resets.