How to override template with block class in Magento 2.2.1

Use this :

<referenceBlock name="page.main.title">
    <action method="setTemplate">
        <argument name="template" xsi:type="string">Vendor_Module::html/title.phtml</argument>
    </action>
</referenceBlock>

To override class using di.xml :

<preference for="Magento\Catalog\Block\Product\View" type="Vendor\ModuleName\Block\Product\View" />

Hope it Helps!