I checked a couple times in different hours and number of characters with the same IP was in
a range from ~15% to ~30%. In peak hours during pvp with FR it can be around 30% but nowhere
near 50% or even 70% like some people say (no idea where such experts get their numbers from
as they have no tools to check anything except current number of characters. Just usual BS.
I just checked log from yesterday at 21:23 CEST - with 211 characters online there was 144 unique
IPs, which probably can be roughly translated to number of players online (so with the largest gangs
relogging like crazy during PvP the alts were about 32% of server).
I'm not saying that it's not a lot. Personally I would prefer server without FR, because it just creates
a huge gap between power gamers and casual players and excludes the latter from PvP. Even with
a hybrid character you might get lucky and win 1 vs 1, but not if the other person has 5 alts over town.