SMP is highly unstable with multiple users on. Tick will jump wildly depending on the activities other users are doing.
Being in the same chunk as a village is almost impossible as the lag spikes through the roof. 300+ tick is not uncommon. Other activites I'm yet to discover are causing these issues. Never experienced any of this in 1.5.2.
And just for reference, had 300+ tick in 1.5.2 when a user built a village breeder and there were over 180 villagers. Same lag in 1.6.1 just from simply ENTERING a village chunk(not same one with 180).
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Is this still a concern in the current Minecraft version? If so, please update the affected versions in order to best aid Mojang ensuring bugs are still valid in the latest releases/pre-releases.