Well Assassins are considered one of the worst class among most expert players, alongside with Snipers IMHO. They happen to have the worst Str cap of 20 which is quite not good when you think about it. They're also complete slaves to the RNG, even more so than most other classes (Beserkers and Swordmasters). Meaning they depend on the RNG to put out critical hits. Especially their skills OHKO/Silencer which happen to be no better than critical hit in a LOT of situations. Meaning they need to relay on killer weapons such as Killing Edge in order to active their OHKO/Silencer skills to be of decent use. Which can hurt your fund ratings since they probably need more just 1 Killing Edge.
On top of that, Assassins are quite a waste of time in FE7 since the earliest point that they're able to promote either of Matthew/Legault is Night of Farewell. Which is quite a tough call between both Matthew and Legault for that only one Fell Contract...Earth Seal won't even work to promote them. Also there aren't any arenas left to arena abuse other than Battle Preparation, but you'll have so little time to train them since the Chpt. only ends in 5 turns. Especially, if your ain't hitting anywhere near a level 20 Assassins. Its also a bad idea to hog all the enemies to either of your protential Assassins while you should be more worry about finishing leveling up your teams. You can also purchase unlimited Fell Contract at Chpt. 30/32 Victory or Death for like what 50000 Golds in a Secret Shop?! So not worth it, seeing as you get another protential Assassins the last minute of the game and you probably wouldn't want to just them. By the time they're already promoted you probably already assembled a good army. Especially if your playing Eliwood's mode since you don't unlock the gaiden chapter on that mode. Playing Hector's mode would be a good opportunity to level up your Assassins if you were to unlock the gaiden chapter in Chpt. 32x. But again it's a waste of time and already assemble your army then. Unless you REALLY like Assassins so much...
I still like Assassins despite the fact...