no, letters are not useless. they are generally not a weapon you use all the time, but there are unquestionably scenarios where letters have been the best tool in the game (tied with phone calls). however, sadly, admins have over time removed these - they used to be great for pulldowns, and for internationals. you basically got DOUBLE the effort for internationals, compared to someone who didnt use letters - thats a massive advantage! actually, i used to use them for long distance (over 1400 miles or whatever) too, they were by a wide margin, the best tool.
i always wondered how many coaches took the time to figure out that 1) you could use unlimited letters, and 2) to figure out that letters and calls were worth a **** ton more than HVs @ 1500. with only 1 other person responding letters, on a poll of 37 (so far), i guess not many! i guess i never really exploited it like i should have in d1, but i thought it would be suspicious if i was recruiting only internationals... thought people might catch on. oh well, it was fun while it lasted!
i dont think there is a home run use for letters now that the 2 home run uses i knew of have been removed. but they aren't useless, either.