Given a username and a domain, perform a lookup on each DC and measure the time it takes (if successful).

Test-DCResponse.ps1

function Test-ADUser() {
[CmdletBinding()]
    <# 
        Perform a user account lookup on a given DC and return a boolean
        indicating success or failure.
    #>
    param(
        [string]$UserName,
        [string]$Server
    )

    try {
        Get-ADUser -Identity $UserName -Server $Server | Out-Null
        return $true
    } catch {
        return $false
    }
}

function Test-DCResponse() {
    <# 
        Find the domain controllers for a given domain, iterate through each one,
        perform a user lookup, measure how much time it took and if it was successful.
    #>
    param(
        [string]$UserName,
        [string]$Domain
    )

    $Servers = Get-ADDomainController -Server $Domain -Filter * | Select-Object -ExpandProperty 'HostName' | Sort-Object
    $Results = @()

    $i=0
    foreach ($Server in $Servers) {
        
        $i+=1
        Write-Progress -Activity 'Testing DC response time...' -Status $Server -PercentComplete ($i / $Servers.count * 100 )

        $Duration = Measure-Command {
            Test-ADUser -UserName $UserName -Server $Server -OutVariable LookupSuccess
        }

        $Results +=  [PSCustomObject] @{
            'HostName' = $Server
            'Success'  = $LookupSuccess[0]
            'Duration' = $Duration
        }
    }

    return $Results
}

function Format-Results() {
    <# 
        Output the timing results to stdout, use color to indicate success or failure.
    #>
    param(
        [PSCustomObject[]]$Results
    )
    
    $OutputPadding = ($Results | Select-Object -ExpandProperty HostName |  Measure-Object -Maximum -Property Length).Maximum + 5
    
    foreach ($Result in $Results) {

        if ($Result.Success) {
            $OutputColor = 'green'
        } else {
            $OutputColor = 'red'
        }
        Write-Host $Result.HostName.PadRight($OutputPadding, '.') -NoNewline
        Write-Host "[$($Result.Duration.ToString())]" -ForegroundColor $OutputColor
    }
}


$Results = Test-DCResponse -UserName 'wile.e.coyote' -Domain 'acme.site' | Sort-Object -Property Duration
Format-Results -Results $Results

Sample output:

ssesvgkm1191.acme.site......[00:00:00.0412119]
IIFIKWHT1101.acme.site......[00:00:00.0462304]
IIFIKWHT1171.acme.site......[00:00:00.0685567]
IIFIKWHT1161.acme.site......[00:00:00.0768323]
IIFIKWHT1110.acme.site......[00:00:00.1871499]
ssesvgkm1117.acme.site......[00:00:00.1922456]
ssesvgkm1119.acme.site......[00:00:00.1952457]
RFYIKWHT1117.acme.site......[00:00:00.1962261]
RFYIKWHT1119.acme.site......[00:00:00.2055862]
WPCIHWHT1116.acme.site......[00:00:00.2077982]
IITINGHT117.acme.site.......[00:00:00.2783724]
IITIKWRHTS119.acme.site.....[00:00:00.3024234]
CYWIZYHT19.acme.site........[00:00:00.3689528]
IIFITAHT1119.acme.site......[00:00:00.3692130]
IIFIFLHT1113.acme.site......[00:00:00.3983722]
ENRIENHT9119.acme.site......[00:00:00.4341225]
ssmssgkm1110.acme.site......[00:00:00.4353417]
IIFISMHT16.acme.site........[00:00:00.4454068]
WIZIWIHT1119.acme.site......[00:00:00.6379755]
IIFIYNHT19.acme.site........[00:00:05.5756056]