Your comments

Here's the quick ST3 plugin that would allow to go to the last tab in the active group:

import sublime, sublime_plugin

class GotolasttabCommand(sublime_plugin.WindowCommand):
	
	def run(self):
		activegroup = self.window.active_group()
		self.window.focus_view(self.window.views_in_group(activegroup)[len(self.window.views_in_group(activegroup)) - 1])