some suggestions when fighting against elves (good for all orc factions), they are 3 times better than your troops, morale, statistics, range, speed, everything except numbers is superior for them, this means you can't (and you are not supposed to, anyway) to play fairly or 1:1 with them, so the first rule ever is:
- never let them group up a full stack, always kill any unit they have roaming around the map, even a single one; groups of 3-5 elven units can be easily dealt with few losses for you with 6-10 orcs unit. Actually it is MUCH better for an orc faction to have two/three small stacks (1/3rd or 1/2) preventing them to gather together; than two full stacks figthing against 1 full elven stack (if they are all elite, you are not even going to win the battle probably, despite fielding 3 or 4 times the numbers of your enemy). Clearly, here and there you'll be forced to fight against a full stack, but this can be managed if:
- never fight battles in which they have the complete edge on the field, like them defending a river crossing or a stone city/castle; they are already too strong for your troops, if they can shot you down effectively before you engage them they'll kick your ass and they do not rout if not surrounded, so a 1st tier unit can hold hundreds and hundreds of orc at the walls. At the same time, avoid to fire the garrison script, no need to spam 3rd or 4th tier units for them, and:
- surround them, with everything you have. Infantry works quite good, but for the best results use wargs and trolls, as they are your sole weapons to really kick them in the mouth; OOG infantry is crap, you can spam billions of snaga stalkers but after the barracks event they will become pretty useless, so treat every OOG infantry unit as anvil for your wargs and trolls; OMM infantry becomes much better after barracks event, still it does not match the elven ones, specially because the best one (halberdiers) are increadibly slow and very subject to arrow fire, so for me they are pretty much harder to be used against elves, because of the general lack of wargs compared to OOG; strategy remains the same, only use some lighter infantry troops to integrate your wargs. A note on trolls: though they are fast and have awesome charge, they are not cavalry, not easy to retreat them from the melee, so charge them on the enemy back line only when your infatry is full engaged; for me the best use anyway is to charge them into enemy archers when they reatreat from the first line after the infantry melee started, honesly wargs are much better (for the numbers, almost 10 times those of the trolls) to be used to charge enemy in the back. Mordor and Isengard have definitely better infantry, but Mordor really lacks cavalry and Isengard, like OMM, can't spam much wargs, so the idea for the first is to group up as much trolls as possible and for the latter to mix lighter infantry (uruk reavers are awesome for this) with wargs to surround the elves.
- kill their generals; charge them with wargs or trolls from the left side (where the general unit is deployed) to maximize chance of killing him; if the general is present or still alive the elves will rout only when they are below 5% of they original number; for the same reason, the first thing you have to avoid absolutely is to get your general killed, especially infantry units are pretty crappy at this.
there could be more to add depending on particular situations, but I think the idea is clear
hope it helps