Sign of apostle, first of all, is to establish churches through preaching. If he or she can do it without acting miracles, then even better so! For neither Lord Himself likes to persuade through miracles (Matthew 16:4).
In fact, the miracles are only auxiliary and if persuasion into faith is possible without miracles, then the latter is better. Thus, if one sees a Christian preacher successful in establishing church without even working miracles and says: "Oh, this preacher is indeed establisher of church, but he is not an apostle, for he worked not a miracle", will be the same as to say: "T.S. Eliot is an author of a great and genial poem the "Wasteland", yet, he is not a poet, for a sign of a poet is to write in rhymes, while Eliot more often than not violates this feature" - sorry, but to write a genial poem is the aim of a poet and main sign of one being a poet; similarly, the main sign of an apostle is to establish a church through preaching. Or imagine a superbly skillful fisherman who can catch fish easily by hands alone; will he be rightfully denied the title of fisherman simply because in some fishermen textbook is written "sign of a fisherman is possession of a fishing net" - no! this is an auxiliary and unnecessary sign, for the sign of a fisherman is a developed skill for catching efficiently fish, which our fisherman does without net, with hands alone.
Who deserves more a name of an apostle: a) a one who works miracles but fails to convert people to Christ or b) a one who does not work miracles but persuades people to convert to Christ and establishes a church? The answer is clear - b)! For the greatest miracle is to persuade men to turn from sins to Christ, or to persuade a Jew through a good and unprejudiced reading of the Holy Writings that the Law and Prophets were a preparation for arrival of the Lord Jesus Christ? Paul did not work miracles, or very rarely, among Jews, but simply discussed Old Testament with them and persuaded them that the promised Messiah was Jesus Christ. Was he not an apostle while doing this?