It sure is very strong, but I think the more interesting question is if Golem/Tunnel alone beats Envoy. It doesn't. Adding one Market makes it close though (better than 2 Markets, to enable cycling your entire deck).
Here's a simple bot that goes Golem/Tunnel + 1 Market:
<player name="Golem/Tunnel" author="Geronimoo" description="Golem with no other actions skips over tunnels, giving you free gold, and acts as a chancellor. Awesome!! Needs a + buy though.">
<type name="UserCreated"/>
<type name="TwoPlayer"/>
<type name="Fun"/>
<type name="Bot"/>
<type name="Combo"/>
<type name="Province"/>
<type name="BigMoney"/>
<buy name="Province"/>
<buy name="Duchy">
<condition>
<left type="gainsNeededToEndGame"/>
<operator type="smallerOrEqualThan" />
<right type="constant" attribute="5.0"/>
</condition>
</buy>
<buy name="Tunnel">
<condition>
<left type="gainsNeededToEndGame"/>
<operator type="smallerOrEqualThan" />
<right type="constant" attribute="4.0"/>
</condition>
</buy>
<buy name="Estate">
<condition>
<left type="gainsNeededToEndGame"/>
<operator type="smallerOrEqualThan" />
<right type="constant" attribute="3.0"/>
</condition>
</buy>
<buy name="Golem">
<condition>
<left type="countCardsInDeck" attribute="Golem"/>
<operator type="smallerThan" />
<right type="constant" attribute="3.0"/>
</condition>
</buy>
<buy name="Tunnel">
<condition>
<left type="countCardsInDeck" attribute="Golem"/>
<operator type="greaterThan" />
<right type="constant" attribute="0.0"/>
</condition>
</buy>
<buy name="Potion">
<condition>
<left type="countCardsInDeck" attribute="Potion"/>
<operator type="smallerThan" />
<right type="constant" attribute="1.0"/>
</condition>
</buy>
<buy name="Market">
<condition>
<left type="countCardsInDeck" attribute="Market"/>
<operator type="equalTo" />
<right type="constant" attribute="0.0"/>
</condition>
</buy>
<buy name="Gold"/>
<buy name="Silver"/>
</player>