This is the tile mapper you have been looking for.
The author is very responsive and takes real care to produce a robust reliable tool, including good documentation. Features like oriented tiles and tile variations can really speed up painting maps once configured.
I initially embarked on a reasonably large platformer project using another tile mapper available in the Assest store, but after hitting some peformance issues and problems with 'broken tilemaps', I switched the project over to using Rotorz system. It does a good job of combining meshes to improve performance where possible, has a range of 'stripping' options to streamline maps by removing unused tile system scripts, depending on your requirements. I haven't yet come across any situation where maps become inconsistent and need to be 'repaired', suggesting the internal data model of Rotorz system is more robust.
Really happy I bought this (and regretting wasting time with other similar tools) - I can easily see it becoming the defacto standard for 2D (and 2.5D) tile mapping within Unity ... it's the 'NGUI' of tile mappers.